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Heat Class 7 MCQ with Answers for Students
At a certain temperature for a given wavelength, the ratio of the emissive power of a body to the emissive power of a black body in the same circumstances is known as
(a) relative emissivity
(b) emissivity
(c) absorption coefficient
(d) coefficient of reflection
Option c – absorption coefficient
When a body is heated, which color corresponds to high temperature
(a) red
(b) yellow
(c) white
(d) orange
Option c – white
If the color of the star is changing from red to blue it means
(a) the star is going away from the earth
(b) the star is coming near the earth
(c) the star is stationary
(d) None of these
Option b – the star is coming near the earth
The radiation emitted by a perfectly black body is proportional to
(a) the temperature on the ideal gas scale
(b) the fourth root of temperature on the ideal gas scale
(c) the fourth power of temperature on the ideal gas scale
(d) square of temperature on an ideal gas scale
Option c – the fourth power of temperature on the ideal gas scale
Newton’s law of cooling is a special case of
(a) Stefan’s law
(b) Kirchhoff’s law
(c) Wien’s law
(d) Plank’s law
Option a – Stefan’s law
Newton’s law of cooling holds good only if the temperature difference between the body and the surrounding is
(a) less than 10°C
(b) more than 10°C
(c) less than 100°C
(d) more than 100°C
Option a – less than 10°C
The first law of thermodynamics expresses
(a) law of conservation of momentum
(b) the law of conservation of energy
(c) the law of conservation of mass
(d) All of the above
Option b – the law of conservation of energy
The first law of thermodynamics is a special case of
(a) Newton’s law
(b) the law of conservation of energy
(c) Charle’s law
(d) the law of heat exchange
Option b – the law of conservation of energy
Thermodynamics is concerned in part with transformations between
(a) different forms of heat energy
(b) internal energy at various temperatures
(c) one form of mechanical energy into other forms
(d) heat, internal energy, and mechanical work
At a given temperature the internal energy of a substance
(a) in the liquid state is equal to that in a gaseous state.
(b) in the liquid state is less than that in a gaseous state.
(c) in the liquid state is more than that in a gaseous state.
(d) is equal for the three states of matter.
Option b – in the liquid state is less than that in a gaseous state
Which of the following is incorrect regarding the first law of thermodynamics?
(a) It is a restatement of the principle of conservation of energy.
(b) It is applicable to cyclic processes
(c) It introduces the concept of entropy
(d) It introduces the concept of internal energy
Option c – It introduces the concept of entropy
The internal energy of an ideal gas does not depend upon
(a) the temperature of the gas
(b) the pressure of the gas
(c) the atomicity of the gas
(d) the number of moles of the gas.
Option b – the pressure of the gas
The air conditioner is based on the principle of
(a) Carnot cycle
(b) refrigerator
(c) the first law of thermodynamics
(d) None of these
Option b – refrigerator
Which of the following processes is reversible?
(a) Transfer of heat by conduction
(b) Transfer of heat by radiation
(c) Isothermal compression
(d) Electrical heating of a nichrome wire
Option c – Isothermal compression
In all natural processes, the entropy of the universe
(a) remains constant
(b) always decreases
(c) always increases
(d) may increase or decrease
Option c – always increases
Which of the following combinations of properties would be most desirable for a cooking pot?
(a) High specific heat and low conductivity
(b) Low specific heat and high conductivity
(c) High specific heat and high conductivity
(d) Low specific heat and low conductivity
Option b – Low specific heat and high conductivity
The temperature at the bottom of a high waterfall is higher than that at the top because
(a) by itself, heat flows from higher to lower temperatures
(b) the difference in height causes a difference in pressure
(c) thermal energy is transformed into mechanical energy
(d) mechanical energy is transformed into thermal energy.
Option d – mechanical energy is transformed into thermal energy
The sprinkling of water slightly reduces the temperature of a closed room because
(a) the temperature of the water is less than that of the room
(b) the specific heat of water is high
(c) water has a large latent heat of vaporization
(d) water is a bad conductor of heat
Option c – water has a large latent heat of vaporization
The temperature of stars is determined by
(a) Stefan’s law
(b) Wien’s displacement law
(c) Kirchhoff’s law
(d) Ohm’s law
Option b – Wien’s displacement law
The fastest mode of transfer of heat is
(a) conduction
(b) convection
(c) radiation
(d) None of these
Option c – radiation
The coefficient of thermal conductivity depends upon
(a) the temperature difference between the two surfaces
(b) area of the plate
(c) material of the plate
(d) All of these
Option c – material of the plate
Good absorbers of heat are
(a) poor emitters
(b) non-emitters
(c) good emitters
(d) highly polished
Option c – good emitters
Which of the following is not close to a black body?
(a) Blackboard paint
(b) Green leaves
(c) Black holes
(d) Red roses
Option a – Blackboard paint
Which of the following statements are true regarding heat? 1. Heat is a form of energy. 2. Heat can be reflected by mirror. 3. Heat is an electromagnetic radiation. 4. Heat cannot pass through a vacuum. Select the correct answer from the codes given :
(a) 1,2 and 3
(b) 2,3 and 4
(c) 1,2 and 4
(d) 1,3 and 4
Option a – 1,2 and 3
Which one of the following statements is correct?
(a) Any energy transfer that does not involve temperature difference in some way is not heat
(b) Any energy transfer always requires a temperature difference
(c) On heating the length and volume of the object remain exactly the same
(d) Whenever there is a temperature difference, heat is the only way of energy transfer
Option a – Any energy transfer that does not involve temperature difference in some way is not heat
Which of the following statements about latent heat for a given substance is/are correct? 1. It is fixed at a given temperature. 2. It depends upon the temperature and volume. 3. it is independent of temperature and volume. 4. It depends on the temperature but independent of volume. Select the correct answer using the code given below :
(a) 2
(b) 1 and 3
(c) 4 only
(d) 1 and 4
Option d – 1 and 4
Which of the following statements about specific heat of a body is/are correct? 1. It depends upon mass and shape of the body 2. It is independent of mass and shape of the body 3. It depends only upon the temperature of the body Select the correct answer using the code given below :
(a) 1 only
(b) 2 and 3
(c) 1 and 3
(d) 2 only
Option a – 1 only
Which one of the following can extinguish fire more quickly?
(a) Cold water
(b) Boiling water
(c) Hot water
(d) Ice
Option b – Boiling water
In which of the following, heat loss is primarily not due to convection?
(a) Boiling water
(b) Land and sea breeze
(c) Circulation of air around blast furnace
(d) Heating of glass surface of a bulb due to current in filament
Option d – Heating of glass surface of a bulb due to current in filament
The working of a microwave oven involves
(a) absorption of microwaves by matter
(b) reception of microwaves by optical fibre
(c) microwave amplification by stimulated emission of radiation
(d) transmission of microwaves through a metal
Option c – microwave amplification by stimulated emission of radiation
Which one of the following statements is not correct?
(a) In the conduction mode of transference of heat, the molecules of solid pass heat from one molecule to another without moving from their positions
(b) The amount of heat required to raise the temperature of a substance is called its specific heat capacity
(c) The process of heat transfer in liquids and gases is through convection mode
(d) The process of heat transfer from a body at higher temperature to a body at lower temperature without heating the space between them is known as radiation
Option b – The amount of heat required to raise the temperature of a substance is called its specific heat capacity
A Kelvin thermometer and a Fahrenheit thermometer both give the same reading for a certain sample. What would be the corresponding reading in a Celsius thermometer?
(a) 574
(b) 301
(c) 273
(d) 232
Option b – 301
The relation PV=RT can describe the behaviour of a real gas at
(a) high temperature and high pressure
(b) high temperature and low pressure
(c) low temperature and low pressure
(d) low temperature and high pressure
Option b – high temperature and low pressure
According to kinetic theory of gases, which one of the following statement(s) is/are true?
(a) Real gas behave as ideal gas at high temperature and low pressure.
(b) Liquid state of ideal gas is impossible
(c) At any temerature and pressure, ideal gas obeys Boyle’s law and charles’ law
(d) The molecules of real gas do not exert any force on one another.
Option a – Real gas behave as ideal gas at high temperature and low pressure
Thermal conductivity of aluminium, copper and stainless steel increases in the order
(a) Copper<Aluminium < Stainless Steel
(b) Stainless Steel < Aluminium <Copper
(c) Aluyminium <Copper < Stainless Steel
(d) Copper < Stainless Steel < Aluminium
Option b – Stainless Steel
Fahrenheit and Celsius are the two scales used for measuring temperature. If the numerical value of a temperature recorded in both the scales is found to be same, what is the temperature?
(a) -40°
(b) +40°
(c) +72°
(d) -72°
Option a – -40°
Two spheres of same size are made of the same metal but one is hollow and the other is solid. They are heated to same temperature, then
(a) both spheres will expand equally
(b) hollow sphere will expand more than the solid one
(c) solid sphere will expand more than the hollow one
(d) none of the above
Option a – both spheres will expand equally
Which one of the following statement is true?
(a) Temperatures differing 25° on the fahrenheit (F) scale must differ by 45° on the celsius (C) scale
(b) 0°F corresponds to -32°C
(c) Temperatures which differ by 10° on the celsius scale must differ by 18° on the Fahrenheit scale
(d) Water at 90°C is warmer than water at 202°F
Option c – Temperatures which differ by 10° on the celsius scale must differ by 18° on the Fahrenheit scale
Which one of the following statements with regard to expansion of materials due to heating is not correct?
(a) As ice melts, it expands uniformly up to 4°C.
(b) Mercury thermometer works using the principle of expansion due to heating.
(c) Small gap is kept between two rails to allow for expansion due to heating.
(d) The length of metallic wire increases when its temperature is increased.
Option a – As ice melts, it expands uniformly up to 4°C
Which one of the following statements is not correct?
(a) Conduction can occur easily in solids, less easily in liquids but hardly at all in gases
(b) Heat energy is carried by moving particles in a convection current
(c) Heat energy is carried by electromagnetic waves in radiation
(d) The temperature at which a solid changes into a liquid is called the boiling point
Option d – The temperature at which a solid changes into a liquid is called the boiling point
If a liquid is heated in space under no gravity, the transfer of heat will take place through a process of
(a) conduction
(b) convection
(c) radiation
(d) can not be heated in the absence of gravity
Option c – radiation
Which zone of a candle flame is the hottest?
(a) Dark innermost zone
(b) Outermost zone
(c) Middle luminous zone
(d) Central zone
Option b – Outermost zone
The evening Sun is not as hot as the midday sun. What is the reason?
(a) In the evening, radiation travel slowly
(b) In the evening, the temperature of the sun decreases
(c) Ozone in the atmosphere absorbs more light in the evening
(d) In the evening, radiation travels a larger distance through the atmosphere
Option d – In the evening, radiation travels a larger distance through the atmosphere
A fan produces a feeling of comfort during hot weather, because
(a) our body radiates more heat into the air
(b) fan supplies cool air
(c) the conductivity of air increases
(d) our perspiration evaporates rapidly
Option d – our perspiration evaporates rapidly
A man with dark skin, in comparison with a man with white skin, will experience
(a) less heat and less cold
(b) less heat and colder
(c) more heat and less cold
(d) more heat and more cold
Option c – more heat and less cold
Compared to a burn due to air at 100°C, a burn due to steam at 100°C is
(a) less dangerous
(b) more dangerous
(c) equally dangerous.
(d) None of these
Option b – more dangerous
Pendulum clocks become slow in summer because
(a) days in summer are large.
(b) of the friction in the coil.
(c) the length of the pendulum increases.
(d) the weight of the pendulum changes.
Option c – the length of the pendulum increases
For Boyle’s law to hold, the gas should be
(a) perfect and of constant mass and temperature
(b) real and of constant mass and temperature
(c) perfect and at constant temperature but variable mass
(d) real and at constant temperature but variable mass
Option a – perfect and of constant mass and temperature
Food in the pressure cooker is cooked faster, as
(a) the boiling point increases due to an increase in pressure
(b) the boiling point decreases due to an increase in pressure
(c) more steam is available at 100°C
(d) more pressure is available at 100°C
Option a – the boiling point increases due to an increase in pressure
A perfect black body has the unique characteristic feature as
(a) a good absorber only
(b) a good radiator only
(c) a good absorber and a good radiator
(d) neither a radiator nor an absorber
Option c – a good absorber and a good radiator
Heat given to a body that raises its temperature by 1°C is known as
(a) water equivalent
(b) thermal capacity
(c) specific heat
(d) temperature gradient
Option c – specific heat
A thermodynamic process where no heat is exchanged with the surroundings is
(a) isothermal
(b) adiabatic
(c) isobaric
(d) isotropic
Option b – adiabatic
Assertion (A): Steam is more harmful to the human body than boiling water in case of a burn. Reason (R): Boiling water contains more heat than steam.
(a) Both A and Rare are true and R is the correct explanation of A
(b) Both A and R are true, but R is not the of A correct explanation
(c) A is true, but R is false
(d) A is false, but R is true
Option c – A is true, but R is false
The deviation of gases from the behavior of ideal gas is due to
(a) colorless molecules
(b) covalent bonding of molecules
(c) attraction of molecules
(d) absolute scale of temp.
Option c – attraction of molecules
The phenomenon of the Brownian movement may be taken as evidence of
(a) the kinetic theory of matter
(b) the electromagnetic theory of radiation
(c) vorpuscular theory of light
(d) the photoelectric phenomenon
Option a – the kinetic theory of matter
The density of water is the highest at the temperature of
(a) 0°C
(b) 4°C
(c) 50°C
(d) 100°C
Option b – 4°C
Which of the following laws was formulated by Nernst?
(a) First Law of Thermodynamics
(b) Second Law of Thermodynamics
(c) Third Law of Thermodynamics
(d) None of the above
Option c – Third Law of Thermodynamics
Transfer of heat by convection can take place in
(a) solids and liquids
(b) solids and vacuum
(c) gases and liquids
(d) vacuum and gases
Option c – gases and liquids
Radiation is the process in which heat is transmitted from one place to another
(a) The substance without the actual motion of the particle
(b) By the actual movement of the vibrating particles
(c) Directly without the necessity of any intervening medium
(d) Through the movement of atoms
Option c – Directly without the necessity of any intervening medium
A piece of ice, 100 g in mass is kept at 0°C. The amount of heat required to melt at 0°C is (take latent heat of melting of ice to be 333.6j/g) :
(a) 750.6 J
(b) 83.4 J
(c) 33360J
(d) 3.336J
Option c – 33360J
The handle of pressure cookers is made of plastic because it should be made non-conductor of heat. The plastic used there is the first man-made plastic, which is :
(a) Polythene
(b) Terylene
(c) Nylon
(d) Bakelite
Option d – Bakelite
Two systems are said to be in thermal equilibrium if and only if :
(a) there can be a heat flow between them even if they are at different temperatures
(b) there cannot be a heat flow between them even if they are at different temperatures
(c) there is no heat flow between them
(d) their temperatures are slightly different
Option c – there is no heat flow between them
The freezer in the refrigerator is located at the top section so that
(a) the entire chamber of the refrigerator is cooled quickly due to convection.
(b) the motor is not heated
(c) the heat gained from the environment is high
(d) the heat gained from the environment is low
Option a – the entire chamber of the refrigerator is cooled quickly due to convection
A: At high altitude regions the cooking of food becomes difficult. B: Water boils at a lower temperature when the pressure is low.
(a) Both A and B are wrong
(b) A and B are correct and B is not the correct explanation of A
(c) A and B are correct and B is the correct explanation of A
(d) A is correct but B is wrong.
Option c – A and B are correct and B is the correct explanation of A
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