A human body has a surface area of approximately 1 m 2 . The normal body temperature is 10 K above the surrounding room temperature T 0 . Take the room temperature to be T 0 = 300 K . For T 0 = 300 K , the value of σ T 4 = 460 W m - 2 (where σ is the Stefan-Boltzmann constant). Which of the following options is/are correct?

Reducing the exposed surface area of the body (e.g. by curling up) allows humans to maintain the same body temperature while reducing the energy lost by radiation.

If the surrounding temperature reduces by a small amount Δ T 0 < < T 0 , then to maintain the same body temperature the same (living) human being needs to radiate Δ W = 4 σ T 0 3 Δ T 0 more energy per unit time

If the body temperature rises significantly then the peak in the spectrum of electromagnetic radiation emitted by the body would shift to longer wavelengths

The amount of energy radiated by the body in 1 second is close to 60 J o u l e s

An incandescent bulb has a thin filament of tungsten that is heated to high temperature by passing an electric current. The hot filament emits black-body radiation. The filament is observed to break up at random locations after a sufficiently long time of operation due to non-uniform evaporation of tungsten from the filament. If the bulb is powered at constant voltage, which of the following statement(s) is(are) true?

The filament consumes less electrical power towards the end of the life of the bulb

The temperature distribution over the filament is uniform

The resistance over small sections of the filament decreases with time

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Two models of a windowpane are made. In one model, two identical glass panes of thickness $3 mm$ are separated with an air gap of $3 mm$ . This composite system is fixed in the window of a room. The other model consists of a single glass pane of thickness $3 mm$ , the temperature difference being the same as for the first model. The ratio of the heat flow for the double pane to that for the single pane is (Given $\frac{K_{thass}}{K_{air}} = 48$ )

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Important Questions on Transmission of Heat

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IMPORTANT

PHYSICS FOR JOINT ENTRANCE EXAMINATION WAVES AND THERMODYNAMICS>Chapter 2 - Transmission of Heat>Exercises>Q 1

During heat exchange, temperature of a solid mass does not change. In this process, heat

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PHYSICS FOR JOINT ENTRANCE EXAMINATION WAVES AND THERMODYNAMICS>Chapter 2 - Transmission of Heat>Exercises>Q 2

A polished metallic piece and a black painted wooden piece are kept in open in bright sun for a long time. Which of the following statements is/are corect?

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PHYSICS FOR JOINT ENTRANCE EXAMINATION WAVES AND THERMODYNAMICS>Chapter 2 - Transmission of Heat>Exercises>Q 3

Choose the correct statements from the following:
(1) Good reflectors are good emitters of thermal radiation
(2) Burns caused by water at $100^{\circ} \mathrm{C}$ are more severe than those caused by steam at $100^{\circ} \mathrm{C}$
(3) If the earth did not have atmosphere, it would become intolerably cold
(4) It is impossible to construct a heat engine of $100 \%$ efficiency

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PHYSICS FOR JOINT ENTRANCE EXAMINATION WAVES AND THERMODYNAMICS>Chapter 2 - Transmission of Heat>Exercises>Q 4

Two bodies

A and B

have thermal emissivities of

0.01 and 0.81

, respectively. The outer surface areas of the two bodies are the same. The two bodies emit total radiant power at the same rate. The wavelength

λ_{B}

corresponding to maximum spectral radiancy in the radiation from

B

shifted from the wavelength corresponding to maximum spectral radiancy in the radiation from

A

1.00 μm

. If the temperature of

A

5802 K

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PHYSICS FOR JOINT ENTRANCE EXAMINATION WAVES AND THERMODYNAMICS>Chapter 2 - Transmission of Heat>Exercises>Q 5

A hollow and a solid sphere of same material and identical outer surface are heated to the same temperature.

HARD

Physics

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PHYSICS FOR JOINT ENTRANCE EXAMINATION WAVES AND THERMODYNAMICS>Chapter 2 - Transmission of Heat>Exercises>Q 6

A heated body emits radiation which has a maximum intensity at frequency

v_{m} .

If the temperature of the body is doubled,

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PHYSICS FOR JOINT ENTRANCE EXAMINATION WAVES AND THERMODYNAMICS>Chapter 2 - Transmission of Heat>Exercises>Q 7

The temperature drop through a two-layer furnace wall is 900^oC. Each layer is of equal area of cross section. Which of the following actions will result in lowering the temperature $θ$ of the interface?

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PHYSICS FOR JOINT ENTRANCE EXAMINATION WAVES AND THERMODYNAMICS>Chapter 2 - Transmission of Heat>Exercises>Q 8

Choose the correct statements from the following:

Important Questions on Transmission of Heat

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