A Text Book of PHYSICS PART I : CLASS 11>Chapter 18 - Heat Transfer>EXERCISE>Q 17

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Calculate the surface temperature of the planet, if the energy radiated by unit area in unit time is $5.67 \times 10^{4} J$ .

Stefan's constant, $σ = 5.67 \times 10^{- 8} W m^{- 2} K^{- 4}$

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Important Questions on Heat Transfer

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A Text Book of PHYSICS PART I : CLASS 11>Chapter 18 - Heat Transfer>EXERCISE>Q 18

The temperature of room heated by a heater is

20 ° C

when outside temperature is

- 20 ° C

and it is

10 ° C

when the outside temperature is

- 40 ° C

. The temperature of the heater is

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A Text Book of PHYSICS PART I : CLASS 11>Chapter 18 - Heat Transfer>EXERCISE>Q 19

A solid copper cube of edges

1 cm

is suspended in an evacuated enclosure. Its temperature is found to fall from

100 ° C

to

99 ° C

in

100 s

. Another solid copper cube of edges

2 cm

, with similar surface nature, is suspended in a similar manner. The time required for this cube to cool from

100 ° C

to

99 ° C

will be approximately.

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A Text Book of PHYSICS PART I : CLASS 11>Chapter 18 - Heat Transfer>EXERCISE>Q 20

Of the following gases, which is known as greenhouse gas.

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A Text Book of PHYSICS PART I : CLASS 11>Chapter 18 - Heat Transfer>EXERCISE>Q 21

The ratio of thermal conductivities of two rods is

4 : 3

. The radius and thermal resistance of both the rods are the same. The ratio of their lengths is

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A Text Book of PHYSICS PART I : CLASS 11>Chapter 18 - Heat Transfer>EXERCISE>Q 22

A bucket of hot water is kept in a room. In

t_{1}

minute the temperature of water falls from

75 ° C

to

70 ° C

, in

t_{2}

minute the temperature falls from

70 ° C

to

65 ° C

and in

t_{3}

minute, the temperature falls from

65 ° C

to

60 ° C

. Here,

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A Text Book of PHYSICS PART I : CLASS 11>Chapter 18 - Heat Transfer>EXERCISE>Q 23

Consider the quantities

(1)

Emissive power and

(2)

Absorptive power.

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A Text Book of PHYSICS PART I : CLASS 11>Chapter 18 - Heat Transfer>EXERCISE>Q 24

Three rods made of same material and having same cross-section have been joined as shown in figure. Each rod has same length. The left and right ends are kept at

0 ° C

and

90 ° C

respectively. What is the temperature of the junction of the three rods will be?

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A Text Book of PHYSICS PART I : CLASS 11>Chapter 18 - Heat Transfer>EXERCISE>Q 25

One end of a metal rod is kept in a boiling water and the other end in melting ice