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A solid sphere of copper of radius $R$ and a hollow sphere of same material of inner radius $r$ and outer radius $R$ are heated to the same temperature and allowed to cool in the same environment. Which of them starts cooling faster?

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Important Questions on Physics

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Agniveer Vayu

IMPORTANT

Achieve Indian Airforce Agniveer Vayu Reasoning and General Awareness Practice Book>Chapter 35 - Physics>Exercise>Q 4

A body cools in $7$ minutes from $60 ° C$ to $40 ° C$ . What will be its temperature after the next $7$ minutes? The temperature of surroundings is $10 ° C$ .

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Achieve Indian Airforce Agniveer Vayu Reasoning and General Awareness Practice Book>Chapter 35 - Physics>Exercise>Q 5

A wire of length

1 m

and radius

10^{- 3} m

is carrying a heavy current and is assumed to radiate as a black body. At equilibrium, its temperature is

900 K

while that of the surroundings is

300 K

. The resistivity of the material of the wire at

300 K

π^{2} \times 10^{- 8} ohm - m

and its temperature coefficient of resistance is

7.8 \times \frac{10^{- 3}}{C^{o}}

. Find the current in the wire. [Given Stefan's constant

= 5.68 \times 10^{- 8} W / m^{2} K^{4}

]

HARD

Agniveer Vayu

IMPORTANT

Achieve Indian Airforce Agniveer Vayu Reasoning and General Awareness Practice Book>Chapter 35 - Physics>Exercise>Q 6

Assuming the sun to be a spherical body of radius

R

at a temperature of

T K

, evaluate the total radiant power, incident on earth, at a distance

r

from the sun - (when radius of earth is

r_{ο}

HARD

Agniveer Vayu

IMPORTANT

Achieve Indian Airforce Agniveer Vayu Reasoning and General Awareness Practice Book>Chapter 35 - Physics>Exercise>Q 7

The graph shown in the adjacent diagram represents the variation of temperature

(T)

of two bodies

x

and

y

having the same surface area, with time (

t

). Both of these bodies lose heat only due to the emission of radiation. Find the correct relation between the emissive and absorptive power of the two bodies.

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Achieve Indian Airforce Agniveer Vayu Reasoning and General Awareness Practice Book>Chapter 35 - Physics>Exercise>Q 8

Assuming the sun to have a spherical outer surface of radius

r

, radiating like a black body at temperature

t ° C

. The power received by a unit surface, (normal to the incident rays) at a distance

R

from the centre of the sun is
(

σ

is the Stefan's constant.)

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IMPORTANT

Achieve Indian Airforce Agniveer Vayu Reasoning and General Awareness Practice Book>Chapter 35 - Physics>Exercise>Q 9

A black body emits radiation at the rate

P

when its temperature is

T

. At this temperature the wavelength at which the radiation has a maximum intensity is

λ_{0}

. If at another temperature

T^{'}

the power radiated is

P^{'}

and wavelength at maximum intensity is

λ_{0} / 2

then

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Achieve Indian Airforce Agniveer Vayu Reasoning and General Awareness Practice Book>Chapter 35 - Physics>Exercise>Q 10

The intensity of radiation emitted by the sun has its maximum value at a wavelength of

510 nm

and that emitted by the north star has the maximum value at

350 nm

. If these stars behave like a black bodies, the ratio of the surface temperature of the sun and the north star is

EASY

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IMPORTANT

Achieve Indian Airforce Agniveer Vayu Reasoning and General Awareness Practice Book>Chapter 35 - Physics>Exercise>Q 1

Which of the following are the characteristic properties of nuclear force :

(i) Nuclear forces are the strongest forces in nature.

(ii) Nuclear forces are independent of charge.

A solid sphere of copper of radius R and a hollow sphere of same material of inner radius r and outer radius R are heated to the same temperature and allowed to cool in the same environment. Which of them starts cooling faster?

Important Questions on Physics

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A solid sphere of copper of radius $R$ and a hollow sphere of same material of inner radius $r$ and outer radius $R$ are heated to the same temperature and allowed to cool in the same environment. Which of them starts cooling faster?