Frank ICSE Physics

Frank ICSE Solutions for Class 9 Physics – Heat: Transmission of Heat

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Frank ICSE Solutions for Class 9 Physics – Heat: Transmission of Heat

PAGE NO: 226
Solution 1:
Conduction, convection and radiation are three modes of transfer of heat.

Solution 2:
The process of conduction involves the transmission of heat from the hot end to the cold end from particle to particle of the medium.

Solution 3:
No, conduction is not possible in vacuum.

Solution 4:
Thermal insulation means restriction of transfer of heat by any means.

Solution 5:
Good conductor allow heat to pass through them easily while bad conductor of heat does not allow heat to pass them.

Solution 6:
No, liquids are poor conductors of heat.

Solution 7:

  • Metals are the best conductor of heat.
  • Gases are the worst conductor of heat.

Solution 8:
Among all the metals, Silver is most conducting.

Solution 9:
Air is most non-conducting.

Solution 10:
No, air is not a good conductor of heat.

Solution 11:
Yes, this is a correct statement. Ebonite and asbestos are worst conductor of heat.

Solution 12:
Cooking utensils are made up of metals because metals are good conductors of heat and they easily allow the heat to pass through them.

Solution 13:
Brick is bad conductor of heat, hence bricks greatly reduce the conduction of heat from outside to the room. In order to ensure better insulation, bricks are made hollow so that air filled between these gaps provides insulation to heat.

Solution 14:
Mercury is good conductor of heat.

Solution 15:
In cold countries, windows have two glass panes and a thin layer of air in between these two glass panes because air is a poor conductor of heat; it obstructs the conduction of heat from the room to the outside.

Solution 16:
Order of increasing heat conductivity:
Air < water< mercury < copper.

Solution 17:

  • Water is heated from below because water is heated by process of convection and in process of convection heat always flows in upward direction from downward direction.
  • In process of convection heat is transferred from one point to another by actual movement of particles of medium and as particles of solid cannot move so process of convection is not possible in case of solids.
  • Conduction is not possible in Vacuum because process of conduction require a material medium for transfer of heat.
  • Inside the refrigerator, cooling takes place by convection. The freezing chamber at the top produces cool and heavy air which descends and hot air from below goes up setting convection current. Thus, cooling in a refrigerator is kept near the top.
  • As earth surface gets heated by sun rays and due to process of convection the air near earth surface open to sunlight get heated while in shade sun rays does not fall on earth surface so air near that surface would not heat up.

Solution 18:
Frank ICSE Solutions for Class 9 Physics - Heat Transmission of Heat 1

Solution 19:
Frank ICSE Solutions for Class 9 Physics - Heat Transmission of Heat 2

PAGE NO : 227
Solution 20:
We receive heat from sun by process of Radiation.

Solution 21:
Radiating power of a surface can be increased by blackening it.

Solution 22:
Heat radiation travels with speed of light and always follows straight path.

Solution 23:
The flask consists of a double walled glass container with vacuum between the walls A and B. The inner side of A and the outer side of B are silvered. It has a narrow mouth which is closed by a non-conducting rubber stopper.
If a hot liquid is placed inside the flask, it cannot lose heat by conduction or convection, as there is no air between the walls. The small amount of heat lost from the liquid by radiation is reflected back into the liquid by silvering of the inner wall A and any radiation striking the outer wall B, is reflected back and prevented from reaching the liquid.

Solution 24:
Green house is a glass house constructed to keep delicate and rare plants that require warmth and protection from weather. It is constructed by panels of glass. The temperature in a green house rises because heat enters the house through the glass but cannot escape out, because the glass reflects the heat back to the inside of the house. This makes glass house warmer than the outside environment.

Solution 25:
Take two sheets of tin plates, one blackened and the other is polished brightly. Fix some drawing pins on the outer side of both sheets using wax. Fix these plates vertically at a very short distance apart. Place a Bunsen burner midway between them. When you light the burner you will observe that the pins from the black painted sheet start dropping while the pins on the polished surface remain in the same position for much longer time.
Thus, we can conclude that black surface is better absorber of heat than the polished one.

Solution 26:

  • As convection require medium for transfer of heat so heat loss due to convection can be minimized if the substance is kept away from any material medium.
  • Similarly for conduction, as conduction also require medium for transfer of heat so heat loss due to conduction can be minimized if the substance is kept away from any material medium.
  • Heat loss due to radiation can be minimized by polishing the surface as polished surfaces radiate less heat.

Solution 27:

  • As no material medium surrounds the ball so there is no possibility of losing heat by conduction or convection. The ball will lose heat by Radiation.
  • Ball will lose minimum amount of heat if it is polished.
  • As loss of heat take place by Radiation and process of radiation does not require any material medium, so there is no role of air in loss of heat.

Solution 28:

  • CFC means Chlorofluorocarbons which are produced mainly by refrigeration industries, aerosol cans, coolants, propellants and plastic foams. They cause global warming.
  • UV means ultraviolet range of radiations. These are the radiations which are emitted by sun and they enter our atmosphere.
  • WHO is World Health Organization which put a check on diseases and global warming etc.

Solution 29:
Green house is a glass house constructed to keep delicate and rare plants that require warmth and protection from weather. It is constructed by panels of glass. The temperature in a green house rises because heat enters the house through the glass but cannot escape out, because the glass reflects the heat back to the inside of the house. This makes glass house warmer than the outside environment. This phenomenon is called green house effect.

Solution 30:
Carbon dioxide, Carbon monoxide, methane are green house gases.

Solution 31:
As fossil fuels are non-renewable sources of energy they are not available again and again if are fully exhausted, so they should not be used extensively.

Solution 32:
Global warming occurs due to the presence of carbon di- oxide, CFCs, methane in the atmosphere. Carbon dioxide acts as a transparent gas to incoming shortwave radiations which the earth re-radiates into space. It therefore traps the outgoing longwave radiations thus warming lower atmosphere of the earth thereby causing global warming.

Solution 33:
Harmful effects of global warming are:

  • The atmospheric temperature of earth would increase thereby making it difficult for a living being to survive.
  • It would melt down the polar caps thus increasing the size of the ocean and leading to floods, tsunami, etc.
  • The increase in temperature would affect climate and rainfall thus affecting flora and fauna.
  • Human beings would be vulnerable to diseases as microbes would get warmth to grow.

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Frank ICSE Solutions for Class 9 Physics – Light: Reflection of Light

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Frank ICSE Solutions for Class 9 Physics – Light: Reflection of Light

PAGE NO: 245
Solution 1:
Light may be defined as the radiant energy which produces in us the sensation of sight. Light itself is invisible but makes other objects visible.

Solution 2:
Yes, light is a form of energy that produces the sensation of vision in our eyes.

Solution 3:
The velocity of light in vacuum is 3 x 108 m/s.

Solution 4:
Two sources of light are

  • Natural, for e.g. Sun
  • Artificial, for e.g. Light bulb.

Solution 5:
Four characteristics of light are :-

  • Light waves can travel through vacuum
  • Light waves are transverse waves
  • Wavelength of light waves is short so that their length is measured in centi-microns.
  • The velocity of light in vacuum is 3 x 108 m/s.

Solution 6:
The Sun and the stars are the two luminous bodies.

Solution 7:
Two non -luminous bodies are moon, chair.

Solution 8:
Frank ICSE Solutions for Class 9 Physics - Light Reflection of Light 1

Solution 9:
A ray of light is the path along which light travels.

Solution 10:
Three distinctions between light and sound waves are

  • Light waves can travel through vacuum while sound waves cannot.
  • Light waves are transverse waves while sound waves are longitudinal waves.
  • The velocity of light in air is 3 x 108 m/s while the speed of light in air is just about 330 m/s.

PAGE NO : 246
Solution 11:

  • A ray of light
  • Divergent beam of light
  • Divergent beam of light
  • Parallel beam of light

Solution 12:
The substance through which light is made to pass is called medium.

Solution 13:
Rectilinear propagation of light is that the light travels along a straight line.

Solution 14:
No, glass is a transparent medium.

Solution 15:
No, no metal is transparent by nature.

Solution 16:
Frank ICSE Solutions for Class 9 Physics - Light Reflection of Light 2

Solution 17:
Waxed paper is the translucent medium among the given substances.

Solution 18:
Frank ICSE Solutions for Class 9 Physics - Light Reflection of Light 3

Solution 19:
Two observations that proves that light travels in a straight line are :-

  • Sunlight coming through a hole in a dark room, we can easily see that light travels in a straight line
  • Light coming from a laser light, used for presentation, can also be seen to travel in straight line.

Solution 20:
When rays of light fall on a surface, they are turned back into the same medium in accordance with some definite laws. This process is known as reflection.

Solution 21:
A smooth and polished flat surface is the cause of regular surface.

Solution 22:
Reflection obeys following two laws

  • The incident ray, the reflected ray, and the normal at the point of incidence, all lie in the same plane.
  • The angle of incidence and the angle of reflection are always equal.

Solution 23:
The height of plane mirror should be half of the size of the object to get a full image of the object. So for a man of height 1.6 m tall should use a 0.8m tall plane mirror.

Solution 24:
Rectilinear propagation of light is that the light travels along a straight line.

Solution 25:
Lateral inversion is the reversal of image experienced in a plane mirror. The image is of the same size and equidistant from the object but the left and right sides are transposed.

Solution 26:
Formation of image is the phenomenon based on laws of reflection.

Solution 27:
The principle employed in a periscope is successive reflections from two plane mirrors.

Solution 28:
The point at which the light is incident on the reflecting surface is called the point of incidence.

Solution 29:
Any smooth, highly polished reflecting surface is called mirror.

Solution 30:
A smooth, highly polished plane surface is called plane mirror.

Solution 31:
The angle between the incident ray and the normal to the surface at the point of incidence is called the angle of incidence.

Solution 32:
Frank ICSE Solutions for Class 9 Physics - Light Reflection of Light 4

Solution 33:
Given, angle between incident ray and mirror = 35°

  • Angle of incidence = angle of mirror to the normal – angle between incident ray and mirror
    = 90 – 35 = 55°
  • Angle of reflection = angle of incidence = 55°
  • Total angle turned = angle of incidence + angle of reflection
    = 55 + 55 = 110°
  • The angle between incident ray and reflected ray = Angle of incidence + Angle of reflection
    = 55 + 55 = 110°

Solution 34:
Given, distance of boy from the mirror = 3 m

  • Distance of image from mirror = distance of boy from the mirror = 3 m
    Distance between boy and his image = distance of boy from the mirror + distance of image from mirror = 3+3 = 6 m
  • Now, distance of boy from the mirror = 4 m
    Distance of image from mirror = 4 m
    Distance between boy and his image = distance of boy from the mirror + distance of image from mirror = 4+4 = 8 m.

Solution 35:
Frank ICSE Solutions for Class 9 Physics - Light Reflection of Light 5

PAGE NO : 247
Solution 36:
Two characteristics of image formed by plane mirror are

  • Image is erect and virtual
  • Image and object are of same size.

Solution 37:
Frank ICSE Solutions for Class 9 Physics - Light Reflection of Light 6

Solution 38:
Frank ICSE Solutions for Class 9 Physics - Light Reflection of Light 7

Solution 39:
Frank ICSE Solutions for Class 9 Physics - Light Reflection of Light 8

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Frank ICSE Solutions for Class 9 Physics – Heat

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Frank ICSE Solutions for Class 9 Physics – Heat

PAGE NO: 191
Solution 1:
Heat is defined as a form of energy which flows from one point to another on account of temperature difference.

Solution 2:
Yes, heat is a form of energy

Solution 3:
Joule is the SI unit of heat.

Solution 4:
One calorie is defined as the quantity of heat required to raise the temperature of 1 gram of water through 1°C.

Solution 5:
1 calorie = 4.2 joules.

Solution 6:
Temperature is the degree of hotness or coldness of a body compared to other bodies around it.
SI unit of temperature is Kelvin (K).

Solution 7:
We feel cold on touching ice because heat flows from our warm hands to cold ice. Due to this flow of heat from hand to ice, the temperature of our hand falls. This is why we feel cold.

Solution 8:
Frank ICSE Solutions for Class 9 Physics - Heat 1

Solution 9:
Heat flows from a body at a higher temperature to a body of lower temperature.

Solution 10:
Yes, heat is the cause of temperature because temperature of a body rises when the heat flows into the body.

Solution 11:
Heat changes the temperature of a body due to flow of heat in or out of the given body.

Solution 12:
Calorie. Because 1 calorie = 4.2 joules.

Solution 13:
No, the exact relation is as given
1 calorie = 4.2 joules.

Solution 14:
Yes, because the heat flow is only due to temperature difference between the temperature of two bodies.

PAGE NO: 229
Solution 1:
Temperature is the degree of hotness or coldness of a body compared to other bodies around it.
SI unit of temperature is Kelvin (K)

Solution 2:
Normal temperature of human body is 37°C.

Solution 3:
To convert 20°c into °F
T°C /100 = (T°f -32)/180
20/100 = (T°f – 32)/180
20 x 180/100 = T°f -32
T°f = 36+32 = 68°F

Solution 4:
Upper fixed point on the Celsius scale is 100°C.

Solution 5:
Tk = 80 K
Tc = Tk -273
Tc = 80 – 273
Tc = -153°C

Solution 6:
SI unit of latent heat is Joule per kg (J/kg).

Solution 7:
Relative humidity is defined as the amount of water vapour in the air compared to the amount needed for saturation.

Solution 8:
Coefficient of Linear expansion is equal to the change in length of a rod of length 1m when its temperature rises by 1°C. Its SI unit is °C-1.

Solution 9:
Celsius was the scientist who discovered the first thermometer in 1710.

Solution 10:
According to principle of calorimetry of mixtures,
Heat gained = Heat lost

Solution 11:
SI unit of coefficient of cubical expansion is °C-1.

Solution 12:
Two uses of bimetallic strip are

  • As thermostat in electric iron
  • As balance wheel in watches

Solution 13:
Telephone wires sag in summer because due to heat of the sun, the wire expands and increases in length, thus they sag in summer.

Solution 14:
Frank ICSE Solutions for Class 9 Physics - Heat 2

Solution 15:
Not all substances expand on heating. Some examples of substances which do not expand on heating are plastics, polythene and rubber.

Solution 16:
Evaporation is the phenomenon of a change of a liquid into vapour without raising the temperature. Evaporation needs energy for phase change from liquid to gases. As water evaporates off your skin, it absorbs energy(heat) from the body to make the phase change to gas thus cooling the body.

Solution 17:
Factors affecting evaporation are

  • Humidity- more the humidity less is the evaporation
  • surface area- more the surface area more is the evaporation
  • wind- more the wind more is the evaporation
  • temperature- more the temperature more is the evaporation

Solution 18:
The cold air that blows from land towards sea during night, is called land breeze
The cold air that blows from the sea towards the land during the day is known as the sea breeze. These breezes are the examples of natural convection current.

Solution 19:
No, the conduction is not possible in gases. Gases are bad conductors.

Solution 20:
No, conduction is not possible in vacuum.

Solution 21:
The velocity of thermal radiations is equal to the speed of light i.e. 3 x 108 m/s.

PAGE NO : 230
Solution 22:
We wear woolen clothes in winter because woolen clothes have tiny pores and air is trapped in these pores and being a bad conductor, the trapped air obstructs the flow of body heat to the surroundings.

Solution 23:
A newly made quilt is warmer than an old one because the cotton in the old quilt gets compressed and very little air will remain trapped in it, hence heat insulation is quite poor.

Solution 24:
In cold countries, water pipes are covered with poor conductors because poor conductor prevents water from freezing and thus prevent these pipes from bursting.

Solution 25:
Three devices used to detect heat radiations are

  • Blackened bulb thermometer
  • Differential air thermo scope
  • Thermopile

Solution 26:
The increase in size of a body on heating is called thermal expansion.

Solution 27:
Linear expansion is the increase in length of a solid on heating.

Solution 28:
Coefficient of Linear expansion is equal to the change in length of a rod of length 1m when its temperature rises by 1°C.

Solution 29:
A bimetallic strip consists of two metal strips- one with high coefficient of expansion and the other with low coefficient of expansion.

Solution 30:
SI unit of coefficient of linear expansion is °C-1.

Solution 31:
Water is the substance which contracts, when heated from 0°C to 4°C.

Solution 32:
Coefficient of volume expansion is equal to the change in volume of a rod of volume 1m3 when its temperature rises by 1°C.

Solution 33:
SI unit of coefficient of volume expansion is °C-1.

Solution 34:
Two uses of bimetallic strip are

  • As thermostat in electric iron
  • As balance wheel in watches

Solution 35:
We should heat the neck of the bottle because due to heating the neck will expand and loosen the stopper stuck in the neck. In this way, we can easily remove the stopper from the bottle.

Solution 36:
When hot water is poured into a thick glass tumbler, it generally cracks because on pouring hot water in the tumbler the inner surface heats up and expands more as compared to its outer surface. This unequal expansion between the two surfaces causes a strain and the tumbler cracks.

Solution 37:
A substance is made up of molecules arranged in a lattice. On heating, the molecules vibrate faster in the lattice and bump into each other harder. So the distance between the molecules increases thus expanding lattice. Thus, the substances expand on heating.

Solution 38:
There are three types of thermal expansion

  • Linear expansion
  • Superficial expansion
  • Cubical expansion

Solution 39:
Gaps are left in the railway tracks because the tracks gets heated during the day and as a result they increase in length. If the gaps are not provided, the railway line would buckle outward and may cause derailment.

Solution 40:
The beams of the bridges expand maximum during the summer days and contract maximum during the winter nights. If the beams are fixed at both ends on the pillars, they may develop crack due to expansion and contraction. To avoid this, beams are made to rest on rollers on the pillars to provide space for expansion.

Solution 41:
Frank ICSE Solutions for Class 9 Physics - Heat 3

Solution 42:
Frank ICSE Solutions for Class 9 Physics - Heat 4

Solution 43:
Frank ICSE Solutions for Class 9 Physics - Heat 5

Solution 44:
A ventilator is provided in a room because it helps in removing the hot air from the room and allows the fresh and cold air to come in.

Solution 45:
No, it is not possible to heat a liquid or gas from above because the transfer of heat through convection takes place vertically upwards in liquids and gases. So if they are heated from above, the liquid or gas at the top will only be heated because most liquids and gases are themselves bad conductor of heat so they cannot conduct heat from top layer to the bottom layer.

Solution 46:

  • Water is heated generally from below because water itself is a bad conductor of heat and the transfer of heat through convection take place vertically upwards.
  • Land becomes warmer than water during the day because water has more specific heat capacity so it absorbs the heat and heats up slowly but on the other hand land has less specific heat and it heats up faster than water.

Solution 47:
Main characteristics of thermometric substance are

  • The substance should have high coefficient of expansion so that it is sensitive to the smallest change in temperature
  • The substance should have uniform expansion all over its entire volume
  • The substance should have minimum specific heat so that it absorbs minimum heat from the body under measurement.

Solution 48:
Wood is an insulator of heat.

Solution 49:

  • In cold countries, windows are provided with two glass panes because in between these two glass panes, a thin layer of air is present: air being a bad conductor obstructs the conduction of heat from the room to outside.
  • 1 calorie = 4.2 joules
  • Yes, it is possible to boil water in a thin paper cup because when heated the heat in the paper cup is transferred to the water through convection and paper cup doesn’t get sufficient heat to get burnt

Solution 50:
Thermometer works on the principle that substances expand on heating and contract on cooling. So we use a thermometric substance which expands and contracts uniformly.

Solution 51:
Advantages of mercury and alcohol as thermometric liquid are

  • They both are good conductors of heat.
  • They have high coefficient of expansion thus are sensitive to the smallest change in temperature
  • Their freezing points are very low and boiling point is high in case of mercury

Disadvantages

  • Alcohol is transparent and this makes hard to read the thermometer.
  • It does not have uniform expansion.
  • Mercury is less sensitive than alcohol as its coefficient of expansion is less than alcohol.
  • Alcohol is a volatile liquid.

Solution 52:
Lower point of a thermometer is the temperature at which ice starts melting at normal atmospheric pressure i.e. 0°C
Upper point of a thermometer is the temperature at which water just starts boiling at normal atmospheric pressure i.e. 100°C.

Solution 53:
Frank ICSE Solutions for Class 9 Physics - Heat 6

Solution 54:

  • Laboratory thermometer is used to measure and observe the temperature of various chemical reactions
  • Clinical thermometer is used to measure human body temperature
  • Six’s maximum and minimum thermometer is used in meteorology and horticulture.

Solution 55:
Frank ICSE Solutions for Class 9 Physics - Heat 7

Solution 56:
The temperature that is common in both clinical and Fahrenheit scale is -40°C
Derivation is as follows
Let the temperature be x
C/100= (F – 32)/180
x/100 = (x-32)/180
x * 180/100 = x-32
9/5 x = x – 32
-4/5 x =32
x = – 40

Solution 57:

  • 60°C
    60/100 = (F-32) / 180
    F = 6 x 18 +32
    = 110°F
  • 100°C
    100/100 = (F – 32) /180
    F = 180 x 1 + 32
    = 212°F
  • -40°C
    -40/100 = (F – 32) /180
    F = -4 x 18 + 32
    = 40°F
  • 85°C
    85/100 = (F – 32) /180
    F = 85 x 18/10 +32
    = 185°F

Solution 58:

  • 104°F
    C = (F – 32) x 100/180
    C = 72 x 100/180
    = 40°C
  • 95°F
    C = (F – 32) x 100/180
    = 63 x 10/18
    = 35°C
  • 113°F
    C = (F – 32) x 100/180
    = 81 x 10/18
    = 45°C
  • 32°F
    C = (F – 32) x 100/180
    = 0 x 10/18
    = 0°C

Solution 59:
Frank ICSE Solutions for Class 9 Physics - Heat 8

Solution 60:
Three modes of heat transfer are

  • Conduction involves the transfer of heat from the hot end to the cold end from particle to particle of the medium.
  • Convection is the transfer of heat from one body to another by actual movement of the particles of the medium
  • Radiation is the transfer of heat from one body to another without the need of an intervening material medium

Solution 61:
Frank ICSE Solutions for Class 9 Physics - Heat 9

Solution 62:
Frank ICSE Solutions for Class 9 Physics - Heat 10

Solution 63:
A wooden knob and a metal latch are both being at same temperature but it feels colder to touch the latch because metal is a good conductor and as soon as we touch it heat from our hand flows to the latch and we feel cold while on the other hand wood is a bad conductor of heat, heat of our hand does not flow into it therefore it does not feel cold.

Solution 64:
The flask consists of double walled glass container with vacuum between the walls A and B to prevent heat loss due to conduction and convection as vacuum is the excellent insulator .to prevent heat loss by radiation, the inner side of the wall A and outer side of wall B is silvered. It has a narrow mouth which is closed by a non-conducting rubber stopper.

Solution 65:
The spiral starts moving because due to the flame of the candle the spiral heats up and expands. While expanding, the spiral tries to create space for the extension in length and an outward pull is created which causes the spiral to move.

Solution 66:

  • In winters, the human body covered with a blanket keeps warm because the blanket has air trapped in it which provide heat insulation to the body from the surroundings and keep us warm
  • It is better to use two thin blankets to keep the body warm rather than using a single blanket of equal thickness because in between the two thin blankets there is more air trapped than in the single blanket of equal thickness so using two thin blankets better heat insulation is provided to the body from the surroundings and keep us warm
  • In winter the birds fluff their feathers in order to trap air in their feathers so that the air provides heat insulation to their body from the surroundings and keep them warm and save them from winter.
  • Old quilts are less warmer than new ones because the cotton in the old quilt gets compressed and very little air will remain trapped in it, hence heat insulation is quite poor
  • People wear light colured clothes in winter because these clothes reflect most of the sun’s radiations and absorb only a little of them. Therefore, they keep themselves cool.

PAGE NO : 231
Solution 67:
Transformation of Sun’s energy in sun-eco system through a food chain is called energy flow.

Solution 68:
Frank ICSE Solutions for Class 9 Physics - Heat 11

Solution 69:
Any energy transfer is not 100% because energy is lost to the surroundings in the form of heat, friction losses during the transfer of energy. Therefore complete energy is not transferred.

Solution 70:
Bio gas is produced by the action of bacteria on decaying organic matter. The primary source of bio gas in villages is dung of cow, or buffalo. The bio gas is mostly methane which can be used as a chief source of light and heat energy.

Solution 71:
Frank ICSE Solutions for Class 9 Physics - Heat 12

Solution 72:
Frank ICSE Solutions for Class 9 Physics - Heat 13

Solution 73:
Frank ICSE Solutions for Class 9 Physics - Heat 14

Solution 74:
Frank ICSE Solutions for Class 9 Physics - Heat 15

PAGE NO : 232
Solution 75:
Frank ICSE Solutions for Class 9 Physics - Heat 16

Solution 76:
Water is not used as a thermometric liquid because It has low coefficient of expansion so it is less sensitive to temperature changes. Moreover, It is transparent thus making it difficult to read the thermometer and water evaporates with time thus producing error and also the freezing and boiling points are also low.

Solution 77:
The sensitivity of a thermometer can be increased by using a substance having high coefficient of expansion and uniform expansion so that its expands with the slightest change in temperature.

Solution 78:

  • When hot water is poured into a thick glass tumbler, it generally cracks because on pouring hot water in the tumbler the inner surface heats up and expands more as compared to its outer surface. This unequal expansion between the two surfaces causes a strain and the tumbler cracks.
  • Pyrex glass tumbler does not crack on adding hot water because Pyrex glass has low coefficient of expansion. It does not expand less when hot water is added to the tumbler.

Solution 79:
Frank ICSE Solutions for Class 9 Physics - Heat 17

Solution 80:
Frank ICSE Solutions for Class 9 Physics - Heat 18

Solution 81:
Frank ICSE Solutions for Class 9 Physics - Heat 19

Solution 82:
Temperature in °C = 1°C
C/100 = (F-32)/180
F = 1 x 18/10 + 32
= 33.8°F

Solution 83:
Lower fixed point = 10°C
Upper fixed point =130°C
Range of thermometer= 130°C – 10°C = 120°C
No of divisions = 100
So least count = 120/100 = 1.2°C
On actual thermometer 40°C would have 40 divisions
So, on this thermometer it would show = 40 x LC = 48°C

Solution 84:
The green house is referred to a glass house. The heat enters the house but cannot escape out, because the glass reflects the heat back to the inside of the house. This makes glass house warmer than the outside environment. This phenomenon is called green house effect.

Solution 85:
Global warming occurs due to the presence of carbon di oxide, CFCs, methane in the atmosphere. Carbon dioxide acts as a transparent gas to incoming shortwave radiations which the earth re-radiates into space. It, therefore traps the outgoing radiations thus warming lower atmosphere of the earth thereby causing global warming.

Solution 86:
Harmful effects of global warming are

  • The atmospheric temperature of earth would increase thereby making it difficult for a living being to survive
  • It would melt down the polar caps thus increasing the size of the ocean and leading to floods, tsunami, etc.
  • The increase in temperature would affect climate and rainfall thus affecting flora and fauna.
  • Human beings would be vulnerable to diseases as microbes would get warmth to grow.

Solution 87:
The temperature in a green house rises because heat enters the house through the glass but cannot escape out, because the glass reflects the heat back to the inside of the house. This makes glass house warmer than the outside environment.

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