Question

Read the following statements:

A. When small temperature difference between a liquid and its surrounding is doubled, the rate of loss of heat of the liquid becomes twice.

B. Two bodies P and Q having equal surface areas are maintained at temperature 10°C and 20°C. The thermal radiation emitted in a given time by P and Q are in the ratio 1 : 1.15.

C. A carnot Engine working between 100 K and 400 K has an efficiency of 75%.

D. When small temperature difference between a liquid and its surrounding is quadrupled, the rate of loss of heat of the liquid becomes twice.

Choose the correct answer from the options given below

• A. A, B, C only
• B. A, B only
• C. A, C only
• D. B, C, D only

Answer 1

Answer: (A)

A, B, C only

Answer 2

The correct option is(A): A, B, C only.

From Newton’s cooling law

$\frac{dq}{dt}=-k(T-T_s)$

so, the statement A is correct

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For B

$u=σeAT^4≅\frac{1}{1.15}$

Statement B is correct

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For C

From Newton’s law of cooling

$\frac{dq}{dt}=-k(T-T_s)$

So, The statement is wrong.