# Engineering Physics Questions and Answers – Thermal Conduction

This set of Engineering Physics Multiple Choice Questions & Answers (MCQs) focuses on “Thermal Conduction”.

1. Clinical thermometer can be sterilized by boiling.
a) True
b) False

Explanation: The range of clinical thermometer is usually from 95°F to 110°F and the boiling point of water is 212°F. So on sterilization by boiling, the capillary of the thermometer will burst due to the thermal expansion of mercury in the capillary.

2. A pressure cooker reduces cooking time for food, because ___________
a) Heat is more evenly distributed in the cooking space
b) The higher pressure inside the cooker crushes the food material
c) Cooking involves chemical changes helped by a rise in temperature
d) Boiling point of water involved in cooking is increased

Explanation: As the pressure inside the pressure cooker increases, the boiling point of water increases.

3. Which of the following is more close to a black body?
a) Blackboard paint
b) Green leaves
c) Black holes
d) Red roses

Explanation: Blackboard paint is close to a black body. A good absorber is a good emitter but a black hole does not emit all radiations.

4. Heat current is maximum in which of the following?
a) Copper
b) Steel and copper
c) Copper and steel
d) Steel

Explanation: Heat current, dQ/dt is proportional to K
As the thermal conductivity of copper is maximum, heat current will be maximum in copper.

5. The sprinkling of water reduces slightly the temperature of a closed room because of ___________
a) Temperature of water is less than that of the room
b) Specific heat of water is high
c) Water has large latent heat of vaporisation
d) Water is a bad conductor of heat

Explanation: Water has a large latent heat of vaporisation. When it is sprinkled over a large area, its vaporisation occurs which, in turn, causes cooling.
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6. At a common temperature, a block of wood and a block of metal feel equally cold or hot. The temperatures of block and wood are ___________
a) Equal to the temperature of the body
b) Less than the temperature of the body
c) Greater than the temperature of the body
d) Has no change

Explanation: The temperature of the block and wood are equal to the temperature of the body as both feel equally hot or cold.

7. On a cold morning, a metal surface will feel colder to touch than a wooden surface, because of ___________
a) Metal has high specific heat
b) Metal has high thermal conductivity
c) Metal has low specific heat
d) Metal has low thermal conductivity

Explanation: Due to the higher thermal conductivity of metal than wood, heat begins to flow readily from our body to the metal surface and so we feel colder.

8. Woollen clothes keep the body warm because of wool ___________
b) Increases the temperature of body
c) Decreases the temperature
d) Has no effect

Explanation: Woollen fibres enclose a large amount of air in them. Both wool and air are bad conductors of heat and do not allow loss of heat from our body due to conduction.

9. Ratio of the amount of heat radiation, transmitted through the body to the amount of heat radiation incident on it, is known as ___________
a) Conductance
b) Inductance
c) Transmittance
d) Absorbance

Explanation: The ratio of an amount of heat transmitted through an object to the amount of heat incident on it is called transmittance.

10. If the amount of heat energy received per unit area from the sun is measured on earth, mars and Jupiter, it will be ___________
a) The same for all
b) In decreasing order Jupiter, Mars, Earth
c) In increasing order Jupiter, Mars, Earth
d) In decreasing order Mars, Earth, Jupiter

Explanation: Heat energy received on a planet varies inversely as the square of the distance from the sun. So Jupiter is lesser than Mars is lesser than Earth.

11. Assertion: For higher temperatures, the peak emission wavelength of a black body shifts to lower wavelengths.
Reason: Peak emission wavelength of black body is proportional to the fourth power of temperatures.
a) Both assertion and reason are true and the reason is the correct explanation of the assertion
b) Both assertion and reason are true but the reason is not a correct explanation of the assertion
c) Assertion is true but the reason is false
d) Both assertion and reason are false

Explanation: The assertion is true but the reason is false. According to Wien’s law, the peak emission wavelength of the body is inversely proportional to the absolute temperature.

12. Assertion: The radiation from the sun’s surface varies as the fourth power of its absolute temperature.
Reason: Sun is not a black body.
a) Both assertion and reason are true and the reason is the correct explanation of the assertion
b) Both assertion and reason are true but the reason is not a correct explanation of the assertion
c) Assertion is true but the reason is false
d) Both assertion and reason are false

Explanation: The assertion is true but the reason is false. At a high temperature of 6000 K, the sun acts like a block body emitting complete radiation. It follows from Stefan’s law that E is proportional to T4

Sanfoundry Global Education & Learning Series – Engineering Physics.

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