UPSC  Physics

1. The temperature of a piece of metal is raised from 27°C to 51.2°C. the rate at which metal radiates energy increases nearly

1.36 times 2.36 times 3.36 times 4.36 times

2. A cup of tea cools from 80°C to 60°C in one minute. The ambient temperature is 30°C. in cooling from 60°C to 50°C, it will take

50 sec 90 sec 60 sec 30 sec

3. Spectrum of a perfectly black body is

Line spectrum Band spectrum Continuous spectrum None of these

4. An object is at the temperature of 400°C. at what temperature would it radiant energy twice as first? The temperature of surrounding may be assumed to be negligible

200°C 200°K 800°C 800°K

5. The process of heat transfer in which heat is transferred with actual migration of medium particles is known as

Conduction Convection Radiation Reflection

6. Which of the following is most repaid process

Conduction Convection Radiation None of these

7. Which of the following will radiate heat to large extent?

Rough surface Polished surface Black rough surface Black polished surface

8. The rate of radiation of black body at 0°C is E watt. The n the rate of radiation of this black body at 273°C will be

16 E 8 E 4 E E

9. Woolen clothes keep the body warm, because wool

Is a bad conductor Increases the temperature of body Decreases the temperature All of these

10. The good absorber of heat are

Non-emitter Poor-emitter Good-emitter Highly polished

 

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