SUMMARY 1. Heat is a form of energy that flows between a body and its surrounding medium by virtue of temperature difference between them. The degree of hotness of the body is quantitatively represented by temperature. 2. A temperature-measuring device (thermometer) makes use of some measurable property (called thermometric property) that changes with temperature. Different thermometers lead to different temperature scales. To construct a temperature scale, two fixed points are chosen and assigned some arbitrary values of temperature. The two numbers fix the origin of the scale and the size of its unit. 3. The Celsius temperature (tC ) and the Fahrenheit temper are (tF )are related by tF = (9/5) tC + 32 4. The ideal gas equation connecting pressure (P), volume (V) and absolute temperature (T) is : PV = µRT where µ is the number of moles and R is the universal gas constant. 5. In the absolute temperature scale, the zero of the scale corresponds to the temperature where every substance in nature has the least possible molecular activity. The Kelvin absolute temperature scale (T ) has the same unit size as the Celsius scale (T2 ), but differs in the origin : TC = T – 273.15 6. The coefficient of linear expansion (αl ) and volume expansion (αv) are defined by the relations : ∆l/l = αl ∆T ∆V/V = αv ∆T where ∆l and ∆V denote the change in length l and volume V for a change of temperature ∆T. The relation between them is : αv = 3 αl 7. The specific heat capacity of a substance is defined by S = 1/m ∆Q/∆T where m is the mass of the substance and ∆Q is the heat required to change its temperature by ∆T. The molar specific heat capacity of a substance is defined by S = 1/(µ ) ∆Q/∆T where µ is the number of moles of the substance. 8. The latent heat of fusion (Lf ) is the heat per unit mass required to change a substance from solid into liquid at the same temperature and pressure. The latent heat of vaporisation (Lv) is the heat per unit mass required to change a substance from liquid to the vapour state without change in the temperature and pressure. 9. The three modes of heat transfer are conduction, convection and radiation. 10. In conduction, heat is transferred between neighbouring parts of a body through molecular collisions, without any flow of matter. For a bar of length L and uniform cross section A with its ends maintained at temperatures T_C and T_Dthe rate of flow of heat H is : H = K A (T_C- T_D)/L where K is the thermal conductivity of the material of the bar. 11. Newton’s Law of Cooling says that the rate of cooling of a body is proportional to the excess temperature of the body over the surroundings : dQ/dt= -k (T_1- T_2) Where T_1 is the temperature of the surrounding medium and T_2 is the temperature of the body.

 Light is a form of energy which produces the sensation of sight.  Speed of light in vacuum / air = 3 × 108 ms–1  Ray of light : A line drawn in the direction of propagation of light is called ray of light.  Beam of light : A group of parallel rays light emitted by a source of light is called beam of light.  Reflection of light : The phenomenon of returning of light in the same medium after striking a surface is called reflection of light.  Laws of reflection : The reflection of light from a surface obeys certain laws called laws of reflection. (i) incident angle is equal to reflected angle i.e. i = r. (ii) Incident ray, reflected ray and normal to the reflecting surface at the point on incident lie in the same plane.  Concave mirror : concave mirror is a part of a hollow sphere whose outer part is silvered and the inner part is reflecting surface.  Convex mirror : convex mirror is a part of a hollow sphere whose outer part is reflecting surface and inner part is silvered.  Centre of curvature : The centre of a hollow sphere of which the spherical mirror forms a part is called centre of curvature. It is denoted by C  Radius of curvature : The radius of a hollow sphere of which the spherical mirror forms a part is called radius of curvature. It is denoted by R  Pole : The mid point of a spherical mirror is called its pole. It is denoted by P  Aperture: The part of spherical mirror exposed to the incident light is called the aperture of the mirror.  Principal Axis: A line joining the centre of curvature (C) and pole (P) of a spherical mirror and extend on either side is called principal axis of the spherical mirror.  Principal Focus : A point on the principal axis of a spherical mirror where the rays of light parallel to the principal axis meet or appears to meet after reflection from the spherical mirror is called principal focus. It is denoted by F.  Focal Plane : A plane normal or perpendicular to the principal axis and passing through the principal focus (F) of the spherical mirror is called focal plane of the spherical mirror.  Focal length (f): The distance between the pole (P) and the principal focus (F) of a spherical mirror is called the focal length of the spherical mirror.  f = , Where R is the radius of the curvature of the mirror.  Focal length and radius of curvature of a concave mirror are negative.  Focal length and radius of curvature of a convex mirror are positive.  Sign Conventions for reflection by spherical mirrors (1) All distance are measured from the pole of a spherical mirror. (2) Distance measured in the direction of incident light are taken as positive. Distance measured in the direction opposite to that of the incident light are taken negative. (3) The upward distance perpendicular to the principal axis are taken as positive, while the downward distance perpendicular to the principal axis are taken as negative.  Radius of curvature plane mirror =  ( infinite)  Focal length of a plane mirror =   Mirror Formula : The relation between u, v, and focal length (f) of a spherical mirror is known as mirror formula. That is  Linear magnification : Linear magnification produced by a mirror is defined as the ratio of the size ( or height) of the image to the size of the object . It is denoted by m. That is  Power of mirror (P) = =  Linear magnification produced by a plane mirror = + 1.  Refraction of light: The bending of light rays when they pass obsessively from one medium to the other medium is called refraction of light .  A transparent medium through which light travels fast is known as optically rarer medium.  A transparent medium through which light travels slow is known as optically denser medium.  Laws of refraction (i) The incident ray, the refracted ray and the normal to the surface separating two media all lie in the same plane. (ii) The ratio of the sine of the incident angle (i) to the sine of the refracted angle (r) is constant i.e. sin i/ sin r = constant This constant is known as the refractive index of second medium w.r.t the first medium.  Absolute refractive index of a medium is defined as the ratio of the speed of light in vacuum (c) to the speed of light in the medium (v) i.e. n = c / v  Relative refractive index of medium. 2 w.r.t. the medium 1 is defined as the ratio of the speed of light in medium 1 (v1) to the speed of light in medium 2 (v2). i.e. n21= v2 / v1

 Light is a form of energy which produces the sensation of sight.  Speed of light in vacuum / air = 3 × 108 ms–1  Ray of light : A line drawn in the direction of propagation of light is called ray of light.  Beam of light : A group of parallel rays light emitted by a source of light is called beam of light.  Reflection of light : The phenomenon of returning of light in the same medium after striking a surface is called reflection of light.  Laws of reflection : The reflection of light from a surface obeys certain laws called laws of reflection. (i) incident angle is equal to reflected angle i.e. i = r. (ii) Incident ray, reflected ray and normal to the reflecting surface at the point on incident lie in the same plane.  Concave mirror : concave mirror is a part of a hollow sphere whose outer part is silvered and the inner part is reflecting surface.  Convex mirror : convex mirror is a part of a hollow sphere whose outer part is reflecting surface and inner part is silvered.  Centre of curvature : The centre of a hollow sphere of which the spherical mirror forms a part is called centre of curvature. It is denoted by C  Radius of curvature : The radius of a hollow sphere of which the spherical mirror forms a part is called radius of curvature. It is denoted by R  Pole : The mid point of a spherical mirror is called its pole. It is denoted by P  Aperture: The part of spherical mirror exposed to the incident light is called the aperture of the mirror.  Principal Axis: A line joining the centre of curvature (C) and pole (P) of a spherical mirror and extend on either side is called principal axis of the spherical mirror.  Principal Focus : A point on the principal axis of a spherical mirror where the rays of light parallel to the principal axis meet or appears to meet after reflection from the spherical mirror is called principal focus. It is denoted by F.  Focal Plane : A plane normal or perpendicular to the principal axis and passing through the principal focus (F) of the spherical mirror is called focal plane of the spherical mirror.  Focal length (f): The distance between the pole (P) and the principal focus (F) of a spherical mirror is called the focal length of the spherical mirror.  f = , Where R is the radius of the curvature of the mirror.  Focal length and radius of curvature of a concave mirror are negative.  Focal length and radius of curvature of a convex mirror are positive.  Sign Conventions for reflection by spherical mirrors (1) All distance are measured from the pole of a spherical mirror. (2) Distance measured in the direction of incident light are taken as positive. Distance measured in the direction opposite to that of the incident light are taken negative. (3) The upward distance perpendicular to the principal axis are taken as positive, while the downward distance perpendicular to the principal axis are taken as negative.  Radius of curvature plane mirror =  ( infinite)  Focal length of a plane mirror =   Mirror Formula : The relation between u, v, and focal length (f) of a spherical mirror is known as mirror formula. That is  Linear magnification : Linear magnification produced by a mirror is defined as the ratio of the size ( or height) of the image to the size of the object . It is denoted by m. That is  Power of mirror (P) = =  Linear magnification produced by a plane mirror = + 1.  Refraction of light: The bending of light rays when they pass obsessively from one medium to the other medium is called refraction of light .  A transparent medium through which light travels fast is known as optically rarer medium.  A transparent medium through which light travels slow is known as optically denser medium.  Laws of refraction (i) The incident ray, the refracted ray and the normal to the surface separating two media all lie in the same plane. (ii) The ratio of the sine of the incident angle (i) to the sine of the refracted angle (r) is constant i.e. sin i/ sin r = constant This constant is known as the refractive index of second medium w.r.t the first medium.  Absolute refractive index of a medium is defined as the ratio of the speed of light in vacuum (c) to the speed of light in the medium (v) i.e. n = c / v  Relative refractive index of medium. 2 w.r.t. the medium 1 is defined as the ratio of the speed of light in medium 1 (v1) to the speed of light in medium 2 (v2). i.e. n21= v2 / v1

 Light is a form of energy which produces the sensation of sight.  Speed of light in vacuum / air = 3 × 108 ms–1  Ray of light : A line drawn in the direction of propagation of light is called ray of light.  Beam of light : A group of parallel rays light emitted by a source of light is called beam of light.  Reflection of light : The phenomenon of returning of light in the same medium after striking a surface is called reflection of light.  Laws of reflection : The reflection of light from a surface obeys certain laws called laws of reflection. (i) incident angle is equal to reflected angle i.e. i = r. (ii) Incident ray, reflected ray and normal to the reflecting surface at the point on incident lie in the same plane.  Concave mirror : concave mirror is a part of a hollow sphere whose outer part is silvered and the inner part is reflecting surface.  Convex mirror : convex mirror is a part of a hollow sphere whose outer part is reflecting surface and inner part is silvered.  Centre of curvature : The centre of a hollow sphere of which the spherical mirror forms a part is called centre of curvature. It is denoted by C  Radius of curvature : The radius of a hollow sphere of which the spherical mirror forms a part is called radius of curvature. It is denoted by R  Pole : The mid point of a spherical mirror is called its pole. It is denoted by P  Aperture: The part of spherical mirror exposed to the incident light is called the aperture of the mirror.  Principal Axis: A line joining the centre of curvature (C) and pole (P) of a spherical mirror and extend on either side is called principal axis of the spherical mirror.  Principal Focus : A point on the principal axis of a spherical mirror where the rays of light parallel to the principal axis meet or appears to meet after reflection from the spherical mirror is called principal focus. It is denoted by F.  Focal Plane : A plane normal or perpendicular to the principal axis and passing through the principal focus (F) of the spherical mirror is called focal plane of the spherical mirror.  Focal length (f): The distance between the pole (P) and the principal focus (F) of a spherical mirror is called the focal length of the spherical mirror.  f = , Where R is the radius of the curvature of the mirror.  Focal length and radius of curvature of a concave mirror are negative.  Focal length and radius of curvature of a convex mirror are positive.  Sign Conventions for reflection by spherical mirrors (1) All distance are measured from the pole of a spherical mirror. (2) Distance measured in the direction of incident light are taken as positive. Distance measured in the direction opposite to that of the incident light are taken negative. (3) The upward distance perpendicular to the principal axis are taken as positive, while the downward distance perpendicular to the principal axis are taken as negative.  Radius of curvature plane mirror =  ( infinite)  Focal length of a plane mirror =   Mirror Formula : The relation between u, v, and focal length (f) of a spherical mirror is known as mirror formula. That is  Linear magnification : Linear magnification produced by a mirror is defined as the ratio of the size ( or height) of the image to the size of the object . It is denoted by m. That is  Power of mirror (P) = =  Linear magnification produced by a plane mirror = + 1.  Refraction of light: The bending of light rays when they pass obsessively from one medium to the other medium is called refraction of light .  A transparent medium through which light travels fast is known as optically rarer medium.  A transparent medium through which light travels slow is known as optically denser medium.  Laws of refraction (i) The incident ray, the refracted ray and the normal to the surface separating two media all lie in the same plane. (ii) The ratio of the sine of the incident angle (i) to the sine of the refracted angle (r) is constant i.e. sin i/ sin r = constant This constant is known as the refractive index of second medium w.r.t the first medium.  Absolute refractive index of a medium is defined as the ratio of the speed of light in vacuum (c) to the speed of light in the medium (v) i.e. n = c / v  Relative refractive index of medium. 2 w.r.t. the medium 1 is defined as the ratio of the speed of light in medium 1 (v1) to the speed of light in medium 2 (v2). i.e. n21= v2 / v1

1. Sound : Sound is a form of energy which produces a sensation of hearing in our ears. 2. Source of sound and its propagation : A source of vibration motion of an object is normally a source of sound. 3. Characteristics of the medium required for the propagation of sound: (i) Medium must be elastic so that the medium particles have the tendency to return back to their original positions after the displacement. (ii) Medium must have the inertia so that its particles have the capacity to store the energy. The frictional resistance of the medium should be negligible to minimise the loss of energy in propagation. 4. Types of waves (i) Mechanical waves : A mechanical wave is a periodic disturbance which requires a material medium for its propagation. On the basis of motion of particles the mechanical waves are classified into two parts. (a) Transverse wave (b) Longitudinal wave (a) Transverse wave : When the particles of the medium vibrate in a direction perpendicular to the direction of propagation of the wave, the wave is known as the transverse wave. For example, waves produced in a stretched string. (b) Longitudinal wave : When the particles of the medium vibrate along the direction of propagation of the wave then the wave is known as the longitudinal wave. For example sound wave in air. (ii) Electromagnetic waves : The waves which do not require medium for propagation are called electromagnetic waves these waves can travel through vacuum also. For example, light waves, X-rays. 5. Characteristics of a sound wave Frequency : The number of vibrations per second is called frequency. The unit of frequency is hertz (ii) Amplitude: The maximum displacement of each particle from its mean position is called amplitude. The S.I. unit of amplitude is metre (m). (iii) Time period: The time taken to complete one vibration is called time period. Frequency= 1/(Time period) or v = 1/T (iv) Wavelength: The distance between two nearest (adjacent) crests or troughs of a wave is called its wavelength. (v) Velocity of wave: The distance travelled by a wave in one second is called velocity of the wave (or speed of the wave). The S.I. unit for the velocity of a wave is metres per second (m/s or ms-1). (vi) Pitch : Pitch is the sensation (brain interpretation) of the frequency of an emitted sound and is the characteristic which distinguishes a shrill (or sharp) sound from a grave (or flat) sound. (vii) Loudness : It is a measure of the sound energy reaching the ear per second. 6. Reflection of sound : When sound waves strike a surface, they return back into the same medium. This phenomenon is called reflection. 7. Laws of reflection : Angle of incidence is equal the angle of reflection. The incident wave, the reflected wave and the normal all lie in the same plane. 8. Echo : Phenomenon of hearing back our own sound is called an echo. It is due to successive reflection from the surfaces obstacles of large size. 9. Relation between speed of sound, time of hearing echo and distance of reflection body :If t is the time at which an echo is heard, d is the distance between the source of sound and the reflecting body and v is the speed of sound. The total distance travelled by the sound is 2d. speed of sound, v = 2d/t or d = vt/2 10. Conditions for the formation of Echoes (i) The minimum distance between the source of sound and the reflecting body should be 17.2 metres. (ii) The wavelength of sound should be less than the height of the reflecting body. (iii) The intensity of sound should be sufficient so that it can be heard after reflection. 11. Reverberation : Persistence of sound after its production is stopped, is called reverberation. A short reverberation is desirable in a concert hall (where music is being played) because it gives ‘life’ to sound. Too much reverberation confuses the programmers and must be reduced to reduce reverberation. 12. Range of Hearing : The audible range of sound for human beings extends from about 20 Hz to 20,000 Hz (one Hz = one cycle/s). Sounds of frequencies below 20 Hz are called infrasonic sound or infrasound. Frequencies higher than 20 kHz are called ultrasonic sound or ultra sound. Ultrasound is produced by dolphins. 13. Applications of ultrasound : The ultrasound is commonly used for medical diagnosis and therapy, and also as a surgical tool. It is also used in a wide variety of industrial applications and processes. Some creatures use ultrasound for information exchange and for the detection and location of objects. Also some bats and porpoises are found to use ultrasound for navi gation and to locate food in darkness or at a place where there is inadequate light for vision (method of search is called echolocation). 14. Sonar : SONAR means Sound Navigation Rang-ing. In this sound waves (ultrasonic) are used [microwaves are absorbed by water)]. Sound waves are emitted by a source. These waves travel in water with velocity v. The waves re-flected by targets (like submarine bottom sea) are detected. Uses (i) The SONAR system is used for detecting the presence of unseen underwater objects, such as a submerged submarine, a sunken ship, sea rock or a hidden iceberg, and locating them accurately. (ii) The principle of SONAR is also used in industry of detection of flaws in metal blocks or sheets without damaging them. 15. Human ear : It is a highly sensitive part of the human body which enables us to hear a sound. It converts the pressure variations in air with audiable frequencies into electric signals which travel to the brain via the auditory nerve. The human ear has three main parts. Their auditory functions are as follows: (i) Outer ear : The outer ear is called `pinna’. It collects the sound from the suri-ounding. The collected sound passes through the auditory canal. At the end of the auditory canal there is a thin membrane called the ear drum or tympanic membrane. When compression of the medium produced due to vibration of the object reaches the ear drum, the pressure on the outside of the membrane increases and forces the eardrum inward. Similarly, the eardrum moves outward when a rarefaction reaches. In this way the ear drum vibrates. (ii) Middle ear: The vibrations are amplified several times by three bones (the hammer, anvil and stirrup) in the middle ear which act as levers. The middle ear transmits the amplified pressure variations received from the sound wave to the inner ear. (iii) Inner ear: In the inner ear, the pressure variations are turned into electrical signals by the cochlea. These electrical signals are sent to the brain via the auditory nerve, and the brain interprets them as sound.

1. Sound : Sound is a form of energy which produces a sensation of hearing in our ears. 2. Source of sound and its propagation : A source of vibration motion of an object is normally a source of sound. 3. Characteristics of the medium required for the propagation of sound: (i) Medium must be elastic so that the medium particles have the tendency to return back to their original positions after the displacement. (ii) Medium must have the inertia so that its particles have the capacity to store the energy. The frictional resistance of the medium should be negligible to minimise the loss of energy in propagation. 4. Types of waves (i) Mechanical waves : A mechanical wave is a periodic disturbance which requires a material medium for its propagation. On the basis of motion of particles the mechanical waves are classified into two parts. (a) Transverse wave (b) Longitudinal wave (a) Transverse wave : When the particles of the medium vibrate in a direction perpendicular to the direction of propagation of the wave, the wave is known as the transverse wave. For example, waves produced in a stretched string. (b) Longitudinal wave : When the particles of the medium vibrate along the direction of propagation of the wave then the wave is known as the longitudinal wave. For example sound wave in air. (ii) Electromagnetic waves : The waves which do not require medium for propagation are called electromagnetic waves these waves can travel through vacuum also. For example, light waves, X-rays. 5. Characteristics of a sound wave Frequency : The number of vibrations per second is called frequency. The unit of frequency is hertz (ii) Amplitude: The maximum displacement of each particle from its mean position is called amplitude. The S.I. unit of amplitude is metre (m). (iii) Time period: The time taken to complete one vibration is called time period. Frequency= 1/(Time period) or v = 1/T (iv) Wavelength: The distance between two nearest (adjacent) crests or troughs of a wave is called its wavelength. (v) Velocity of wave: The distance travelled by a wave in one second is called velocity of the wave (or speed of the wave). The S.I. unit for the velocity of a wave is metres per second (m/s or ms-1). (vi) Pitch : Pitch is the sensation (brain interpretation) of the frequency of an emitted sound and is the characteristic which distinguishes a shrill (or sharp) sound from a grave (or flat) sound. (vii) Loudness : It is a measure of the sound energy reaching the ear per second. 6. Reflection of sound : When sound waves strike a surface, they return back into the same medium. This phenomenon is called reflection. 7. Laws of reflection : Angle of incidence is equal the angle of reflection. The incident wave, the reflected wave and the normal all lie in the same plane. 8. Echo : Phenomenon of hearing back our own sound is called an echo. It is due to successive reflection from the surfaces obstacles of large size. 9. Relation between speed of sound, time of hearing echo and distance of reflection body :If t is the time at which an echo is heard, d is the distance between the source of sound and the reflecting body and v is the speed of sound. The total distance travelled by the sound is 2d. speed of sound, v = 2d/t or d = vt/2 10. Conditions for the formation of Echoes (i) The minimum distance between the source of sound and the reflecting body should be 17.2 metres. (ii) The wavelength of sound should be less than the height of the reflecting body. (iii) The intensity of sound should be sufficient so that it can be heard after reflection. 11. Reverberation : Persistence of sound after its production is stopped, is called reverberation. A short reverberation is desirable in a concert hall (where music is being played) because it gives ‘life’ to sound. Too much reverberation confuses the programmers and must be reduced to reduce reverberation. 12. Range of Hearing : The audible range of sound for human beings extends from about 20 Hz to 20,000 Hz (one Hz = one cycle/s). Sounds of frequencies below 20 Hz are called infrasonic sound or infrasound. Frequencies higher than 20 kHz are called ultrasonic sound or ultra sound. Ultrasound is produced by dolphins. 13. Applications of ultrasound : The ultrasound is commonly used for medical diagnosis and therapy, and also as a surgical tool. It is also used in a wide variety of industrial applications and processes. Some creatures use ultrasound for information exchange and for the detection and location of objects. Also some bats and porpoises are found to use ultrasound for navi gation and to locate food in darkness or at a place where there is inadequate light for vision (method of search is called echolocation). 14. Sonar : SONAR means Sound Navigation Rang-ing. In this sound waves (ultrasonic) are used [microwaves are absorbed by water)]. Sound waves are emitted by a source. These waves travel in water with velocity v. The waves re-flected by targets (like submarine bottom sea) are detected. Uses (i) The SONAR system is used for detecting the presence of unseen underwater objects, such as a submerged submarine, a sunken ship, sea rock or a hidden iceberg, and locating them accurately. (ii) The principle of SONAR is also used in industry of detection of flaws in metal blocks or sheets without damaging them. 15. Human ear : It is a highly sensitive part of the human body which enables us to hear a sound. It converts the pressure variations in air with audiable frequencies into electric signals which travel to the brain via the auditory nerve. The human ear has three main parts. Their auditory functions are as follows: (i) Outer ear : The outer ear is called `pinna’. It collects the sound from the suri-ounding. The collected sound passes through the auditory canal. At the end of the auditory canal there is a thin membrane called the ear drum or tympanic membrane. When compression of the medium produced due to vibration of the object reaches the ear drum, the pressure on the outside of the membrane increases and forces the eardrum inward. Similarly, the eardrum moves outward when a rarefaction reaches. In this way the ear drum vibrates. (ii) Middle ear: The vibrations are amplified several times by three bones (the hammer, anvil and stirrup) in the middle ear which act as levers. The middle ear transmits the amplified pressure variations received from the sound wave to the inner ear. (iii) Inner ear: In the inner ear, the pressure variations are turned into electrical signals by the cochlea. These electrical signals are sent to the brain via the auditory nerve, and the brain interprets them as sound.

1. Sound : Sound is a form of energy which produces a sensation of hearing in our ears. 2. Source of sound and its propagation : A source of vibration motion of an object is normally a source of sound. 3. Characteristics of the medium required for the propagation of sound: (i) Medium must be elastic so that the medium particles have the tendency to return back to their original positions after the displacement. (ii) Medium must have the inertia so that its particles have the capacity to store the energy. The frictional resistance of the medium should be negligible to minimise the loss of energy in propagation. 4. Types of waves (i) Mechanical waves : A mechanical wave is a periodic disturbance which requires a material medium for its propagation. On the basis of motion of particles the mechanical waves are classified into two parts. (a) Transverse wave (b) Longitudinal wave (a) Transverse wave : When the particles of the medium vibrate in a direction perpendicular to the direction of propagation of the wave, the wave is known as the transverse wave. For example, waves produced in a stretched string. (b) Longitudinal wave : When the particles of the medium vibrate along the direction of propagation of the wave then the wave is known as the longitudinal wave. For example sound wave in air. (ii) Electromagnetic waves : The waves which do not require medium for propagation are called electromagnetic waves these waves can travel through vacuum also. For example, light waves, X-rays. 5. Characteristics of a sound wave Frequency : The number of vibrations per second is called frequency. The unit of frequency is hertz (ii) Amplitude: The maximum displacement of each particle from its mean position is called amplitude. The S.I. unit of amplitude is metre (m). (iii) Time period: The time taken to complete one vibration is called time period. Frequency= 1/(Time period) or v = 1/T (iv) Wavelength: The distance between two nearest (adjacent) crests or troughs of a wave is called its wavelength. (v) Velocity of wave: The distance travelled by a wave in one second is called velocity of the wave (or speed of the wave). The S.I. unit for the velocity of a wave is metres per second (m/s or ms-1). (vi) Pitch : Pitch is the sensation (brain interpretation) of the frequency of an emitted sound and is the characteristic which distinguishes a shrill (or sharp) sound from a grave (or flat) sound. (vii) Loudness : It is a measure of the sound energy reaching the ear per second. 6. Reflection of sound : When sound waves strike a surface, they return back into the same medium. This phenomenon is called reflection. 7. Laws of reflection : Angle of incidence is equal the angle of reflection. The incident wave, the reflected wave and the normal all lie in the same plane. 8. Echo : Phenomenon of hearing back our own sound is called an echo. It is due to successive reflection from the surfaces obstacles of large size. 9. Relation between speed of sound, time of hearing echo and distance of reflection body :If t is the time at which an echo is heard, d is the distance between the source of sound and the reflecting body and v is the speed of sound. The total distance travelled by the sound is 2d. speed of sound, v = 2d/t or d = vt/2 10. Conditions for the formation of Echoes (i) The minimum distance between the source of sound and the reflecting body should be 17.2 metres. (ii) The wavelength of sound should be less than the height of the reflecting body. (iii) The intensity of sound should be sufficient so that it can be heard after reflection. 11. Reverberation : Persistence of sound after its production is stopped, is called reverberation. A short reverberation is desirable in a concert hall (where music is being played) because it gives ‘life’ to sound. Too much reverberation confuses the programmers and must be reduced to reduce reverberation. 12. Range of Hearing : The audible range of sound for human beings extends from about 20 Hz to 20,000 Hz (one Hz = one cycle/s). Sounds of frequencies below 20 Hz are called infrasonic sound or infrasound. Frequencies higher than 20 kHz are called ultrasonic sound or ultra sound. Ultrasound is produced by dolphins. 13. Applications of ultrasound : The ultrasound is commonly used for medical diagnosis and therapy, and also as a surgical tool. It is also used in a wide variety of industrial applications and processes. Some creatures use ultrasound for information exchange and for the detection and location of objects. Also some bats and porpoises are found to use ultrasound for navi gation and to locate food in darkness or at a place where there is inadequate light for vision (method of search is called echolocation). 14. Sonar : SONAR means Sound Navigation Rang-ing. In this sound waves (ultrasonic) are used [microwaves are absorbed by water)]. Sound waves are emitted by a source. These waves travel in water with velocity v. The waves re-flected by targets (like submarine bottom sea) are detected. Uses (i) The SONAR system is used for detecting the presence of unseen underwater objects, such as a submerged submarine, a sunken ship, sea rock or a hidden iceberg, and locating them accurately. (ii) The principle of SONAR is also used in industry of detection of flaws in metal blocks or sheets without damaging them. 15. Human ear : It is a highly sensitive part of the human body which enables us to hear a sound. It converts the pressure variations in air with audiable frequencies into electric signals which travel to the brain via the auditory nerve. The human ear has three main parts. Their auditory functions are as follows: (i) Outer ear : The outer ear is called `pinna’. It collects the sound from the suri-ounding. The collected sound passes through the auditory canal. At the end of the auditory canal there is a thin membrane called the ear drum or tympanic membrane. When compression of the medium produced due to vibration of the object reaches the ear drum, the pressure on the outside of the membrane increases and forces the eardrum inward. Similarly, the eardrum moves outward when a rarefaction reaches. In this way the ear drum vibrates. (ii) Middle ear: The vibrations are amplified several times by three bones (the hammer, anvil and stirrup) in the middle ear which act as levers. The middle ear transmits the amplified pressure variations received from the sound wave to the inner ear. (iii) Inner ear: In the inner ear, the pressure variations are turned into electrical signals by the cochlea. These electrical signals are sent to the brain via the auditory nerve, and the brain interprets them as sound.

Electric current : An electric current is defined as the amount of charge flowing through any cross-section of a conductor per unit time, I = . Electric current is a scalar quantity.  Electric current in terms of number of electrons (n) in a conductor, I = , e = charge on an electron = –1.6 × 10–19 C.  In a metallic wire or conductor, the flow of electric current is due to the flow of electrons from one end to the other end of the wire.  Charge carrier in a metallic wire are conduction elements.  6.25 × 1018 electrons make one coulomb of charge.  S.I. unit of electric current is ampere (A).  Ampere (A) : Electric current through a conductor is said to be 1 ampere if one coulomb charge flows through any cross-section of the conductor in one second.  Ammeter is used to measure electric current.  Ammeter is always connected in series in an electric circuit.  Electric potential is defined as work done per unit charge. V =  Electric potential is a scalar quantity.  Electric potential difference is defined as the work done in moving a unit positive charge from one point to another point. dV =  SI unit of electric potential is volt (V).  Voltmeter is used to measure the potential difference between two points in an electric circuit.  Voltmeter is always connected in parallel in an electric circuit.  Ohm's Law : This law states that, "the electric current flowing in a conductor is directly proportional to the potential difference across the ends of the conductor, provided the temperature and other physical conditions of the conductor remain the same".  Resistance (R) : Resistance of a conductor is the ability of the conductor to oppose the flow of charge through it.  Unit of resistance is ohm.  1 Ohm : Resistance of a conductor is said to be 1 ohm if a potential difference of 1 volt across the ends of the conductor produces a current of 1 ampere through it. Resistor is a component (say a metallic wire) in an electric circuit which offers resistance to the flow of electrons constituting the electric current in the electric circuit.  Law of Resistance : (i) Resistance of a conductor depends upon the nature of the material of the conductor. (ii) Resistance of a conductor is directly proportional to the length of the conductor. (iii) Resistance of a conductor is inversely proportional to the each of cross-section of the conductor. (iv) Resistance of metallic conductor increases with the increase of temperature and decreases with the decrease of the temperature.  R =  Resistivity or Specific Resistance () : Resistivity is defined as the resistance of the conductor of unit length and unit area of cross-section.  Unit of Resistivity : In CGS system, unit if resistivity is ohm-cm. In SI system, unit of resistivity is ohm-metre.  Two or more resistors are said to be connected in series if same amount of current flows through these resistors.  The effective resistance of series combination of resistors is the algebraic sum of the individual resistances of the resistors in the combination.  An electric bulb or a heater or a metallic wire acts as a resistor.  If one of the electric bulbs connected in a series is fused, then no electric bulb will glow inspite of the fact that the combination is connected with a source of electric current.  Two or more resistors are said to be connected in parallel if the potential difference across each resistor is equal to the applied potential difference across the combination of the resistors.  The effective resistance of the resistors connected in parallel is less than the minimum resistance of a resistor in the combination.  Resistors are connected in series if the resistance of the electric circuit is to be increased.  Resistors are connected in parallel if the resistance of the electric circuit is to be decreased.  Joule's Law of Heating : The amount of heat produced in a conductor is (i) Directly proportional to the square of the electric current flowing through it. (ii) Directly proportional to the resistance of the conductor. (iii) Directly proportional to the time for which the electric current flows through the conductor. H = I2Rt (joule)  Electric fuse is a safety device used to save the electric appliances from burning.  Electric fuse is a wire made of a material having low melting point.  Electric fuse wire is made of copper or tin-lead alloy.  Electric energy : The work done by a source of electricity to maintain a current in an electric circuit is known as electric energy. E = VIt  Electric power : Electric power is defined as the amount of electric work done in one second. P = VI = I2R = V2 / R  SI unit of power is watt.  Practical unit of power is horse power (h.p.) 1 h.p. = 746 W  Electric energy = Electric power × time  Commercial unit of Energy : kilowatt-hour (kWh)  1 kWh = 3.6 × 106 J

Electric current : An electric current is defined as the amount of charge flowing through any cross-section of a conductor per unit time, I = . Electric current is a scalar quantity.  Electric current in terms of number of electrons (n) in a conductor, I = , e = charge on an electron = –1.6 × 10–19 C.  In a metallic wire or conductor, the flow of electric current is due to the flow of electrons from one end to the other end of the wire.  Charge carrier in a metallic wire are conduction elements.  6.25 × 1018 electrons make one coulomb of charge.  S.I. unit of electric current is ampere (A).  Ampere (A) : Electric current through a conductor is said to be 1 ampere if one coulomb charge flows through any cross-section of the conductor in one second.  Ammeter is used to measure electric current.  Ammeter is always connected in series in an electric circuit.  Electric potential is defined as work done per unit charge. V =  Electric potential is a scalar quantity.  Electric potential difference is defined as the work done in moving a unit positive charge from one point to another point. dV =  SI unit of electric potential is volt (V).  Voltmeter is used to measure the potential difference between two points in an electric circuit.  Voltmeter is always connected in parallel in an electric circuit.  Ohm's Law : This law states that, "the electric current flowing in a conductor is directly proportional to the potential difference across the ends of the conductor, provided the temperature and other physical conditions of the conductor remain the same".  Resistance (R) : Resistance of a conductor is the ability of the conductor to oppose the flow of charge through it.  Unit of resistance is ohm.  1 Ohm : Resistance of a conductor is said to be 1 ohm if a potential difference of 1 volt across the ends of the conductor produces a current of 1 ampere through it. Resistor is a component (say a metallic wire) in an electric circuit which offers resistance to the flow of electrons constituting the electric current in the electric circuit.  Law of Resistance : (i) Resistance of a conductor depends upon the nature of the material of the conductor. (ii) Resistance of a conductor is directly proportional to the length of the conductor. (iii) Resistance of a conductor is inversely proportional to the each of cross-section of the conductor. (iv) Resistance of metallic conductor increases with the increase of temperature and decreases with the decrease of the temperature.  R =  Resistivity or Specific Resistance () : Resistivity is defined as the resistance of the conductor of unit length and unit area of cross-section.  Unit of Resistivity : In CGS system, unit if resistivity is ohm-cm. In SI system, unit of resistivity is ohm-metre.  Two or more resistors are said to be connected in series if same amount of current flows through these resistors.  The effective resistance of series combination of resistors is the algebraic sum of the individual resistances of the resistors in the combination.  An electric bulb or a heater or a metallic wire acts as a resistor.  If one of the electric bulbs connected in a series is fused, then no electric bulb will glow inspite of the fact that the combination is connected with a source of electric current.  Two or more resistors are said to be connected in parallel if the potential difference across each resistor is equal to the applied potential difference across the combination of the resistors.  The effective resistance of the resistors connected in parallel is less than the minimum resistance of a resistor in the combination.  Resistors are connected in series if the resistance of the electric circuit is to be increased.  Resistors are connected in parallel if the resistance of the electric circuit is to be decreased.  Joule's Law of Heating : The amount of heat produced in a conductor is (i) Directly proportional to the square of the electric current flowing through it. (ii) Directly proportional to the resistance of the conductor. (iii) Directly proportional to the time for which the electric current flows through the conductor. H = I2Rt (joule)  Electric fuse is a safety device used to save the electric appliances from burning.  Electric fuse is a wire made of a material having low melting point.  Electric fuse wire is made of copper or tin-lead alloy.  Electric energy : The work done by a source of electricity to maintain a current in an electric circuit is known as electric energy. E = VIt  Electric power : Electric power is defined as the amount of electric work done in one second. P = VI = I2R = V2 / R  SI unit of power is watt.  Practical unit of power is horse power (h.p.) 1 h.p. = 746 W  Electric energy = Electric power × time  Commercial unit of Energy : kilowatt-hour (kWh)  1 kWh = 3.6 × 106 J

Electric current : An electric current is defined as the amount of charge flowing through any cross-section of a conductor per unit time, I = . Electric current is a scalar quantity.  Electric current in terms of number of electrons (n) in a conductor, I = , e = charge on an electron = –1.6 × 10–19 C.  In a metallic wire or conductor, the flow of electric current is due to the flow of electrons from one end to the other end of the wire.  Charge carrier in a metallic wire are conduction elements.  6.25 × 1018 electrons make one coulomb of charge.  S.I. unit of electric current is ampere (A).  Ampere (A) : Electric current through a conductor is said to be 1 ampere if one coulomb charge flows through any cross-section of the conductor in one second.  Ammeter is used to measure electric current.  Ammeter is always connected in series in an electric circuit.  Electric potential is defined as work done per unit charge. V =  Electric potential is a scalar quantity.  Electric potential difference is defined as the work done in moving a unit positive charge from one point to another point. dV =  SI unit of electric potential is volt (V).  Voltmeter is used to measure the potential difference between two points in an electric circuit.  Voltmeter is always connected in parallel in an electric circuit.  Ohm's Law : This law states that, "the electric current flowing in a conductor is directly proportional to the potential difference across the ends of the conductor, provided the temperature and other physical conditions of the conductor remain the same".  Resistance (R) : Resistance of a conductor is the ability of the conductor to oppose the flow of charge through it.  Unit of resistance is ohm.  1 Ohm : Resistance of a conductor is said to be 1 ohm if a potential difference of 1 volt across the ends of the conductor produces a current of 1 ampere through it. Resistor is a component (say a metallic wire) in an electric circuit which offers resistance to the flow of electrons constituting the electric current in the electric circuit.  Law of Resistance : (i) Resistance of a conductor depends upon the nature of the material of the conductor. (ii) Resistance of a conductor is directly proportional to the length of the conductor. (iii) Resistance of a conductor is inversely proportional to the each of cross-section of the conductor. (iv) Resistance of metallic conductor increases with the increase of temperature and decreases with the decrease of the temperature.  R =  Resistivity or Specific Resistance () : Resistivity is defined as the resistance of the conductor of unit length and unit area of cross-section.  Unit of Resistivity : In CGS system, unit if resistivity is ohm-cm. In SI system, unit of resistivity is ohm-metre.  Two or more resistors are said to be connected in series if same amount of current flows through these resistors.  The effective resistance of series combination of resistors is the algebraic sum of the individual resistances of the resistors in the combination.  An electric bulb or a heater or a metallic wire acts as a resistor.  If one of the electric bulbs connected in a series is fused, then no electric bulb will glow inspite of the fact that the combination is connected with a source of electric current.  Two or more resistors are said to be connected in parallel if the potential difference across each resistor is equal to the applied potential difference across the combination of the resistors.  The effective resistance of the resistors connected in parallel is less than the minimum resistance of a resistor in the combination.  Resistors are connected in series if the resistance of the electric circuit is to be increased.  Resistors are connected in parallel if the resistance of the electric circuit is to be decreased.  Joule's Law of Heating : The amount of heat produced in a conductor is (i) Directly proportional to the square of the electric current flowing through it. (ii) Directly proportional to the resistance of the conductor. (iii) Directly proportional to the time for which the electric current flows through the conductor. H = I2Rt (joule)  Electric fuse is a safety device used to save the electric appliances from burning.  Electric fuse is a wire made of a material having low melting point.  Electric fuse wire is made of copper or tin-lead alloy.  Electric energy : The work done by a source of electricity to maintain a current in an electric circuit is known as electric energy. E = VIt  Electric power : Electric power is defined as the amount of electric work done in one second. P = VI = I2R = V2 / R  SI unit of power is watt.  Practical unit of power is horse power (h.p.) 1 h.p. = 746 W  Electric energy = Electric power × time  Commercial unit of Energy : kilowatt-hour (kWh)  1 kWh = 3.6 × 106 J

 Hans Christian oersted discovered a relationship between electricity and magnetism.  A current carrying wire behaves as a magnet.  When a current passes through a wire, a magnetic field is set up around the wire. This effect of current is called magnetic effect of current.  Like magnetic poles repel each other and unlike magnetic poles attract each other.  Magnetic field is space or region around a current carrying wire or a magnet within which its influence is felt by another magnet.  Magnetic field line : The path along which a free unit north pole moves in a magnetic field is called magnetic field line. The tangent at any point on a magnetic field line gives the direction of the magnetic field at that point.  Two magnetic field lines can't intersect or cross each other.  Magnetic field lines are crowded in a region of strong magnetic field.  Magnetic field lines are far apart in a region of weak magnetic field.  When current passes through a straight wire or conductor, a magnetic field is set up around the wire or conductor.  Magnetic field around a current carrying wire or conductor is represented by concentric circles centred at the wire or the conductor.  The direction of magnetic field around the current carrying conductor is determined by Right Hand Thumb Rule.  Magnetic field around a current carrying wire increases with the increase in the current passing through the wire.  Magnetic field around a current carrying wire or conductor is represented by concentric circles centred at the wire or the conductor.  The direction of magnetic field around the current carrying conductor is determined by Right Hand Thumb Rule.  Magnetic field around a current carrying wire increases with the increase in the current passing through the wire.  Magnetic field around a current carrying wire decreases as we go away from the wire.  Magnetic field due to a very long wire like a power transmission line carrying current I and at a distance r from the wire is given by B = ; where, µ0 = 4 × 10–7 TmA–1  Two parallel wires or conductors carrying current in the same directs attract each other.  Two parallel wires or conductors carrying current in the opposite directions repel each other.  The magnetic field around a straight current carrying conductor or wire can be increased by bending it into a circular loop.  The strength of magnetic field produced at the centre of a circular loop of a wire is (i) directly proportional to the amount of current passing through the loop of the wire. (ii) directly proportional to the number of turns of the circular loop of the wire. (iii) inversely proportional to the radius of the circular loop of the wire.  Magnetic field produced by a current carrying circular wire or loop decreases on both sides along the axis of the circular wire.  A solenoid is a coil of many turns of an insulated copper wire closely wound in the shape of a tight spring.  Magnetic field inside a current carrying solenoid is uniform magnetic field.  A solenoid carrying current behaves like a bar magnet.  A soft iron rod placed in a current carrying solenoid is known as electromagnet.  A current carrying conductor placed perpendicular to the magnetic field experience a force.  The force acting on a current carrying conductor placed perpendicular to the magnetic field B is given by F = BIl  Direction of force experienced by a current carrying conductor placed in a magnetic field is determined by Fleming’s Left Hand Rule.  No Force acts on a current carrying conductor when placed parallel to the magnetic field.  SI unit of magnetic field is tesla (T).  Force acts on a charge moving perpendicular to the magnetic field. This force is called Lorentz force.  Force acting on a charge Q moving with velocity v perpendicular to the magnetic field B is given by F = BQV  No force acts on a charge moving parallel to the magnetic field B.  Direction of force experienced by a moving charge in a magnetic field is determined by Right Hand Rule.  Electric motor is a device which converts electrical energy into mechanical energy.  Principle of electric motor : Electric motor works on the principle that a current carrying conductor placed perpendicular to a magnetic field experiences a force.  The phenomenon of producing induced current in a closed circuit due to the change in magnetic field in the circuit is known as electromagnetic induction.  More induced current flows through a closed coil if a bar magnet is brought towards or away from the coil with large speed.  No induced current flows through a closed coil if magnetic field linked with it does not change.  Direction of induced current in a conductor is determined by Fleming’s Right hand rule.  Direct current is an electric current whose magnitude is either constant or variable but the direction of flow in a conductor remains the same.  Frequency of direct current is zero.  Alternating current is an electric current whose magnitude changes with time and direction reverse periodically.  In India, frequency of A.C. is 50 Hz.  A.C. is more dangerous than D.C.  Electric generator is a device used to convert mechanical energy into electrical energy.  Electric generator works on the principle of electromagnetic induction.  To supply electric power from one place to another place, three wires known as phase wire (or live wire), neutral wire and earth wire are used.  The potential difference between the live wire and neutral wire in a household supply of electric power is 220 V.  Current rating of a fuse is the maximum amount of electric current that can be passed through the fuse wire without melting it.  Current rating of a fuse wire in a circuit having bulbs and tubes is 5A.  Current rating of a fuse wire in a circuit having heating appliances is 15A.  Electric fuse is a safety device used to save the electrical appliances from burning when large current flows in the circuit.  Electric fuse is made of a material of low melting point.  Material used for making a fuse wire is made of copper / aluminium / tin-lead alloy.  Short Circuiting : When live wire and neutral wire come in direct contact, the resistance of the circuit becomes very small. Hence huge current flows through the circuit. This huge current produces large amount of heat in the circuit and the circuit catches fire. This is known as short circuiting.

 Hans Christian oersted discovered a relationship between electricity and magnetism.  A current carrying wire behaves as a magnet.  When a current passes through a wire, a magnetic field is set up around the wire. This effect of current is called magnetic effect of current.  Like magnetic poles repel each other and unlike magnetic poles attract each other.  Magnetic field is space or region around a current carrying wire or a magnet within which its influence is felt by another magnet.  Magnetic field line : The path along which a free unit north pole moves in a magnetic field is called magnetic field line. The tangent at any point on a magnetic field line gives the direction of the magnetic field at that point.  Two magnetic field lines can't intersect or cross each other.  Magnetic field lines are crowded in a region of strong magnetic field.  Magnetic field lines are far apart in a region of weak magnetic field.  When current passes through a straight wire or conductor, a magnetic field is set up around the wire or conductor.  Magnetic field around a current carrying wire or conductor is represented by concentric circles centred at the wire or the conductor.  The direction of magnetic field around the current carrying conductor is determined by Right Hand Thumb Rule.  Magnetic field around a current carrying wire increases with the increase in the current passing through the wire.  Magnetic field around a current carrying wire or conductor is represented by concentric circles centred at the wire or the conductor.  The direction of magnetic field around the current carrying conductor is determined by Right Hand Thumb Rule.  Magnetic field around a current carrying wire increases with the increase in the current passing through the wire.  Magnetic field around a current carrying wire decreases as we go away from the wire.  Magnetic field due to a very long wire like a power transmission line carrying current I and at a distance r from the wire is given by B = ; where, µ0 = 4 × 10–7 TmA–1  Two parallel wires or conductors carrying current in the same directs attract each other.  Two parallel wires or conductors carrying current in the opposite directions repel each other.  The magnetic field around a straight current carrying conductor or wire can be increased by bending it into a circular loop.  The strength of magnetic field produced at the centre of a circular loop of a wire is (i) directly proportional to the amount of current passing through the loop of the wire. (ii) directly proportional to the number of turns of the circular loop of the wire. (iii) inversely proportional to the radius of the circular loop of the wire.  Magnetic field produced by a current carrying circular wire or loop decreases on both sides along the axis of the circular wire.  A solenoid is a coil of many turns of an insulated copper wire closely wound in the shape of a tight spring.  Magnetic field inside a current carrying solenoid is uniform magnetic field.  A solenoid carrying current behaves like a bar magnet.  A soft iron rod placed in a current carrying solenoid is known as electromagnet.  A current carrying conductor placed perpendicular to the magnetic field experience a force.  The force acting on a current carrying conductor placed perpendicular to the magnetic field B is given by F = BIl  Direction of force experienced by a current carrying conductor placed in a magnetic field is determined by Fleming’s Left Hand Rule.  No Force acts on a current carrying conductor when placed parallel to the magnetic field.  SI unit of magnetic field is tesla (T).  Force acts on a charge moving perpendicular to the magnetic field. This force is called Lorentz force.  Force acting on a charge Q moving with velocity v perpendicular to the magnetic field B is given by F = BQV  No force acts on a charge moving parallel to the magnetic field B.  Direction of force experienced by a moving charge in a magnetic field is determined by Right Hand Rule.  Electric motor is a device which converts electrical energy into mechanical energy.  Principle of electric motor : Electric motor works on the principle that a current carrying conductor placed perpendicular to a magnetic field experiences a force.  The phenomenon of producing induced current in a closed circuit due to the change in magnetic field in the circuit is known as electromagnetic induction.  More induced current flows through a closed coil if a bar magnet is brought towards or away from the coil with large speed.  No induced current flows through a closed coil if magnetic field linked with it does not change.  Direction of induced current in a conductor is determined by Fleming’s Right hand rule.  Direct current is an electric current whose magnitude is either constant or variable but the direction of flow in a conductor remains the same.  Frequency of direct current is zero.  Alternating current is an electric current whose magnitude changes with time and direction reverse periodically.  In India, frequency of A.C. is 50 Hz.  A.C. is more dangerous than D.C.  Electric generator is a device used to convert mechanical energy into electrical energy.  Electric generator works on the principle of electromagnetic induction.  To supply electric power from one place to another place, three wires known as phase wire (or live wire), neutral wire and earth wire are used.  The potential difference between the live wire and neutral wire in a household supply of electric power is 220 V.  Current rating of a fuse is the maximum amount of electric current that can be passed through the fuse wire without melting it.  Current rating of a fuse wire in a circuit having bulbs and tubes is 5A.  Current rating of a fuse wire in a circuit having heating appliances is 15A.  Electric fuse is a safety device used to save the electrical appliances from burning when large current flows in the circuit.  Electric fuse is made of a material of low melting point.  Material used for making a fuse wire is made of copper / aluminium / tin-lead alloy.  Short Circuiting : When live wire and neutral wire come in direct contact, the resistance of the circuit becomes very small. Hence huge current flows through the circuit. This huge current produces large amount of heat in the circuit and the circuit catches fire. This is known as short circuiting.

Movement & Locomotion - (i) Functions of human skeleton (ii) Axial and Appendicular Skeleton (iii) Types of joints - immovable, slightly movable and freely movable (hinge joint, ball and socket joint, gliding joint, pivot joint.) (c) Structure and functions of skin. Various parts of the skin and their functions to be taught with the help of diagrams; heat regulation, vasodilation, vasoconstriction to be explained.

Respiratory System: Organs; mechanism of breathing; tissue respiration, heat production. Differences between anaerobic respiration in plants and in man. Brief idea of respiratory volumes, effect of altitude on breathing and asphyxiation should be taught. Role of diaphragm and intercostals muscles in breathing must be explained to provide a clear idea of breathing process. Brief idea of gaseous transport and tissue respiration to be given.

Respiratory System: Organs; mechanism of breathing; tissue respiration, heat production. Differences between anaerobic respiration in plants and in man. Brief idea of respiratory volumes, effect of altitude on breathing and asphyxiation should be taught. Role of diaphragm and intercostals muscles in breathing must be explained to provide a clear idea of breathing process. Brief idea of gaseous transport and tissue respiration to be given.

Respiratory System: Organs; mechanism of breathing; tissue respiration, heat production. Differences between anaerobic respiration in plants and in man. Brief idea of respiratory volumes, effect of altitude on breathing and asphyxiation should be taught. Role of diaphragm and intercostals muscles in breathing must be explained to provide a clear idea of breathing process. Brief idea of gaseous transport and tissue respiration to be given.

Structure and functions of skin. Various parts of the skin and their functions to be taught with the help of diagrams; heat regulation, vasodilation, vasoconstriction to be explained.

Nutrition (i) Classes of food: balanced diet. Malnutrition and deficiency diseases. Functions of carbohydrates, fats, proteins, mineral salts (calcium, iodine, iron and sodium), vitamins and water in proper functioning of the body to be discussed. Sources of vitamins their functions and deficiency diseases to be discussed. Students should be familiar with the term ‘Balanced Diet’. Importance of cellulose in our diet should be discussed. Students should be taught about Kwashiorkor and Marasmus. (ii) the structure of a tooth, different types of teeth. Structure of a tooth to be discussed with the help of a diagram. Functions of different types of teeth must also be taught. (iii) Digestive System: Organs and digestive glands and their functions (including enzymes and their functions in digestion; absorption, utilisation of digested food); tests for reducing sugar, starch, protein and fats. Organs and their functions; functions of saliva; brief idea of peristalsis; digestion in various parts of alimentary canal. Tests for sugar, starch, protein and fats.

Nutrition (i) Classes of food: balanced diet. Malnutrition and deficiency diseases. Functions of carbohydrates, fats, proteins, mineral salts (calcium, iodine, iron and sodium), vitamins and water in proper functioning of the body to be discussed. Sources of vitamins their functions and deficiency diseases to be discussed. Students should be familiar with the term ‘Balanced Diet’. Importance of cellulose in our diet should be discussed. Students should be taught about Kwashiorkor and Marasmus. (ii) the structure of a tooth, different types of teeth. Structure of a tooth to be discussed with the help of a diagram. Functions of different types of teeth must also be taught. (iii) Digestive System: Organs and digestive glands and their functions (including enzymes and their functions in digestion; absorption, utilisation of digested food); tests for reducing sugar, starch, protein and fats. Organs and their functions; functions of saliva; brief idea of peristalsis; digestion in various parts of alimentary canal. Tests for sugar, starch, protein and fats.

Nutrition (i) Classes of food: balanced diet. Malnutrition and deficiency diseases. Functions of carbohydrates, fats, proteins, mineral salts (calcium, iodine, iron and sodium), vitamins and water in proper functioning of the body to be discussed. Sources of vitamins their functions and deficiency diseases to be discussed. Students should be familiar with the term ‘Balanced Diet’. Importance of cellulose in our diet should be discussed. Students should be taught about Kwashiorkor and Marasmus. (ii) the structure of a tooth, different types of teeth. Structure of a tooth to be discussed with the help of a diagram. Functions of different types of teeth must also be taught. (iii) Digestive System: Organs and digestive glands and their functions (including enzymes and their functions in digestion; absorption, utilisation of digested food); tests for reducing sugar, starch, protein and fats. Organs and their functions; functions of saliva; brief idea of peristalsis; digestion in various parts of alimentary canal. Tests for sugar, starch, protein and fats.

Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula H 2. It is colorless, odorless, tasteless, non-toxic, and highly combustible.

periodic table, in full periodic table of the elements, in chemistry, the organized array of all the chemical elements in order of increasing atomic number—i.e., the total number of protons in the atomic nucleus.

periodic table, in full periodic table of the elements, in chemistry, the organized array of all the chemical elements in order of increasing atomic number—i.e., the total number of protons in the atomic nucleus.

periodic table, in full periodic table of the elements, in chemistry, the organized array of all the chemical elements in order of increasing atomic number—i.e., the total number of protons in the atomic nucleus.

gas laws, laws that relate the pressure, volume, and temperature of a gas. Boyle's law—named for Robert Boyle—states that, at constant temperature, the pressure P of a gas varies inversely with its volume V, or PV = k, where k is a constant.

gas laws, laws that relate the pressure, volume, and temperature of a gas. Boyle's law—named for Robert Boyle—states that, at constant temperature, the pressure P of a gas varies inversely with its volume V, or PV = k, where k is a constant.

gas laws, laws that relate the pressure, volume, and temperature of a gas. Boyle's law—named for Robert Boyle—states that, at constant temperature, the pressure P of a gas varies inversely with its volume V, or PV = k, where k is a constant.

gas laws, laws that relate the pressure, volume, and temperature of a gas. Boyle's law—named for Robert Boyle—states that, at constant temperature, the pressure P of a gas varies inversely with its volume V, or PV = k, where k is a constant.

The Language Of Chemistry Or Chemical Equations, published in 2010, is a book that covers different types of chemical equations. Chemistry is a branch of science that deals with the interaction of atoms and different types of energy.

The Language Of Chemistry Or Chemical Equations, published in 2010, is a book that covers different types of chemical equations. Chemistry is a branch of science that deals with the interaction of atoms and different types of energy.

The Language Of Chemistry Or Chemical Equations, published in 2010, is a book that covers different types of chemical equations. Chemistry is a branch of science that deals with the interaction of atoms and different types of energy.

The Language Of Chemistry Or Chemical Equations, published in 2010, is a book that covers different types of chemical equations. Chemistry is a branch of science that deals with the interaction of atoms and different types of energy.

The Language Of Chemistry Or Chemical Equations, published in 2010, is a book that covers different types of chemical equations. Chemistry is a branch of science that deals with the interaction of atoms and different types of energy.

The Language Of Chemistry Or Chemical Equations, published in 2010, is a book that covers different types of chemical equations. Chemistry is a branch of science that deals with the interaction of atoms and different types of energy.

The Language Of Chemistry Or Chemical Equations, published in 2010, is a book that covers different types of chemical equations. Chemistry is a branch of science that deals with the interaction of atoms and different types of energy.

Its chemical formula, H 2O, indicates that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. The hydrogen atoms are attached to the oxygen atom at an angle of 104.45°. "Water" is also the name of the liquid state of H2O at standard temperature and pressure.

In a chemical change, a new compound is formed but in a physical change, the substance changes its state of existence. Atoms or ions or molecules which react to form a new substance are called reactants; the new atoms or molecules formed are products. A chemical reaction follows the law of conservation of mass.

In a chemical change, a new compound is formed but in a physical change, the substance changes its state of existence. Atoms or ions or molecules which react to form a new substance are called reactants; the new atoms or molecules formed are products. A chemical reaction follows the law of conservation of mass.

In a chemical change, a new compound is formed but in a physical change, the substance changes its state of existence. Atoms or ions or molecules which react to form a new substance are called reactants; the new atoms or molecules formed are products. A chemical reaction follows the law of conservation of mass.

In a chemical change, a new compound is formed but in a physical change, the substance changes its state of existence. Atoms or ions or molecules which react to form a new substance are called reactants; the new atoms or molecules formed are products. A chemical reaction follows the law of conservation of mass.

A chemical bond is a bond that holds atoms together. It is the force that binds ions or molecules together. It helps form a chemical compound. Examples of the chemical compounds that are of special interest to biologists are water, sodium chloride, and carbon dioxide

A chemical bond is a bond that holds atoms together. It is the force that binds ions or molecules together. It helps form a chemical compound. Examples of the chemical compounds that are of special interest to biologists are water, sodium chloride, and carbon dioxide

A chemical bond is a bond that holds atoms together. It is the force that binds ions or molecules together. It helps form a chemical compound. Examples of the chemical compounds that are of special interest to biologists are water, sodium chloride, and carbon dioxide

A chemical bond is a bond that holds atoms together. It is the force that binds ions or molecules together. It helps form a chemical compound. Examples of the chemical compounds that are of special interest to biologists are water, sodium chloride, and carbon dioxide