Q.1 Which of the following is the primary mode of heat transfer in metals?
Conduction
Convection
Radiation
Evaporation
Explanation - Metals have free electrons that transfer kinetic energy rapidly, making conduction the primary mode of heat transfer.
Correct answer is: Conduction
Q.2 The SI unit of heat is:
Joule
Calorie
Watt
Newton
Explanation - Heat is a form of energy, and its SI unit is the Joule (J).
Correct answer is: Joule
Q.3 The amount of heat required to raise the temperature of 1 kg of water by 1°C is called:
Specific heat capacity
Latent heat
Thermal conductivity
Calorific value
Explanation - Specific heat capacity is the amount of heat required to raise 1 kg of a substance by 1°C.
Correct answer is: Specific heat capacity
Q.4 Which law governs the rate of heat conduction through a solid?
Newton's law of cooling
Fourier's law
Stefan-Boltzmann law
Planck's law
Explanation - Fourier's law states that the rate of heat transfer through a material is proportional to the negative gradient of temperature and the area.
Correct answer is: Fourier's law
Q.5 Which of the following materials is a poor conductor of heat?
Copper
Aluminium
Wood
Silver
Explanation - Wood is an insulating material and has low thermal conductivity, making it a poor conductor.
Correct answer is: Wood
Q.6 Latent heat of fusion refers to:
Heat required to melt a unit mass of solid at its melting point
Heat required to vaporize a unit mass of liquid at its boiling point
Heat required to raise the temperature by 1°C
Heat lost during cooling
Explanation - Latent heat of fusion is the energy needed to change 1 kg of solid into liquid without temperature change.
Correct answer is: Heat required to melt a unit mass of solid at its melting point
Q.7 Which mode of heat transfer does not require a medium?
Conduction
Convection
Radiation
Advection
Explanation - Radiation transfers heat through electromagnetic waves and does not require any medium.
Correct answer is: Radiation
Q.8 Newton's law of cooling states that:
Rate of cooling is proportional to temperature of the body
Rate of cooling is proportional to difference in temperature between body and surroundings
Rate of cooling is proportional to square of temperature difference
Rate of cooling is constant
Explanation - Newton's law of cooling states that the rate of heat loss is proportional to the temperature difference with the surroundings.
Correct answer is: Rate of cooling is proportional to difference in temperature between body and surroundings
Q.9 Calorimetry is the study of:
Measurement of temperature
Measurement of heat
Heat conduction
Heat radiation
Explanation - Calorimetry involves measuring the amount of heat absorbed or released during physical or chemical processes.
Correct answer is: Measurement of heat
Q.10 Which of the following has the highest thermal conductivity?
Copper
Air
Water
Wood
Explanation - Copper is a metal with very high thermal conductivity compared to air, water, and wood.
Correct answer is: Copper
Q.11 The energy required to change 1 kg of liquid into vapor at constant temperature is called:
Latent heat of fusion
Latent heat of vaporization
Specific heat
Thermal energy
Explanation - Latent heat of vaporization is the heat required to convert 1 kg of liquid into gas at its boiling point.
Correct answer is: Latent heat of vaporization
Q.12 The process of heat transfer in fluids due to bulk motion is called:
Conduction
Convection
Radiation
Diffusion
Explanation - Convection is heat transfer in liquids and gases by the bulk movement of the fluid.
Correct answer is: Convection
Q.13 Which of the following statements about radiation is correct?
Requires a medium to transfer heat
Cannot occur in vacuum
Depends on surface color and temperature
Only occurs in solids
Explanation - Radiative heat transfer depends on the surface's emissivity, color, and temperature.
Correct answer is: Depends on surface color and temperature
Q.14 Specific heat of water is approximately:
1 cal/g°C
4.18 J/g°C
Both a and b
0.5 cal/g°C
Explanation - 1 cal/g°C is equivalent to 4.18 J/g°C, so both are correct expressions for water's specific heat.
Correct answer is: Both a and b
Q.15 A good insulator of heat has:
High thermal conductivity
Low thermal conductivity
High density
High specific heat
Explanation - Low thermal conductivity prevents heat from passing through easily, making it a good insulator.
Correct answer is: Low thermal conductivity
Q.16 The principle of calorimetry is based on:
Conservation of energy
Conservation of momentum
Newton's third law
Fourier's law
Explanation - Calorimetry relies on the conservation of energy, where heat lost by hot body equals heat gained by cold body.
Correct answer is: Conservation of energy
Q.17 Which of the following increases the rate of heat loss by convection?
Decreasing temperature difference
Increasing fluid velocity
Using a solid conductor
Reducing fluid motion
Explanation - Faster fluid movement increases convective heat transfer due to enhanced mixing.
Correct answer is: Increasing fluid velocity
Q.18 The quantity of heat lost or gained by a body is proportional to its mass, specific heat, and change in temperature. This is expressed as:
Q = mcΔT
Q = mL
Q = kAΔT/d
Q = σAT^4
Explanation - This is the formula for sensible heat: Q = mcΔT, where m is mass, c is specific heat, and ΔT is temperature change.
Correct answer is: Q = mcΔT
Q.19 Which of the following has the highest latent heat of vaporization?
Water
Ethanol
Mercury
Benzene
Explanation - Water has a very high latent heat of vaporization (approx. 2260 J/g) compared to other liquids.
Correct answer is: Water
Q.20 The process of heat transfer in a gas by random motion of molecules is called:
Conduction
Convection
Diffusion
Radiation
Explanation - In gases, conduction occurs due to molecular collisions transferring kinetic energy.
Correct answer is: Conduction
Q.21 Black body radiation depends primarily on:
Color and temperature
Density
Pressure
Specific heat
Explanation - A black body's emissive power depends on its temperature and surface color (ideally black).
Correct answer is: Color and temperature
Q.22 Which of the following will cool fastest in air?
A hot metal ball
A hot wooden ball
A hot plastic ball
All cool at same rate
Explanation - Metal has high thermal conductivity, so it transfers heat to air faster and cools quickly.
Correct answer is: A hot metal ball
Q.23 The heat required to raise the temperature of a given mass of a substance by 1°C is called:
Specific heat
Calorific value
Latent heat
Thermal conductivity
Explanation - Specific heat is the heat required per unit mass to raise the temperature by 1°C.
Correct answer is: Specific heat
Q.24 Which material would you use to minimize heat loss from a container?
Copper
Aluminium
Glass wool
Steel
Explanation - Glass wool is an excellent insulator with very low thermal conductivity.
Correct answer is: Glass wool
Q.25 If the heat lost by a hot object equals the heat gained by a cold object, the system is considered:
Non-adiabatic
Adiabatic
Isothermal
Calorimetrically balanced
Explanation - In calorimetry, when heat lost equals heat gained, the system is calorimetrically balanced.
Correct answer is: Calorimetrically balanced