1. Two bars of copper having same length but an equal diameter are heated to the same temperature. The change in length will be:

2. The earth intercepts approximately one billionth of the power radiated by the sun. if the surface temperature of the sun were to drop by a factor of 2, the average radiant energy incident on earth per second would reduce by factor of

3. Thermal equilibrium implies equality of:

4. Gas thermometers are more sensitive than liquid thermometers as the gases

5. 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

6. The running of fan makes us comfortable during summer because it:

7. Heat is associated with

8. Co-efficient of reflection, coefficient of absorption and coefficient transmission are related as

9. A metallic ball has a spherical cavity at its centre. If the ball is heated, what happens to the cavity?

10. The good absorber of heat are

11. A black body at hot temperature at 227°C radiates heat at a rate of 5 cal/cm²s. at a temperature of 727°C the rate of heat radiated per unit area will be

12. Two blocks of ice when pressed together join to form one block. This happens because

13. The earth receives at its surface radiation from the sun at the rate of 1400 W/m². the distance of the centre of the sun from the surface of the earth is 1.5 1011 m and the radius of the sun is 7.0 108 m. treating sun as a black body, it follows from the above data that its surface temperature is,

14. Emissivity of perfectly black body is

15. The top of lake is frozen as the atmospheric temperature is -10°C. The temperature at the bottom of the lake is most likely to be

16. Unit of Stefans constant is given by

17. A bimetallic strip is made of aluminium and steel (α_Al > α_steel). On heating, the strip will

18. As the temperature is increased, the time period of a pendulum

19. A surface at temperature T0°K receives power P by radiation from a small sphere at temperature T >> T0 and at a distance d. if both T and d are doubled, the power received by surface will becomes approximately

20. The temperature determines the direction of net change of: