1. Heat is associated with

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

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

4. Emissivity of perfectly black body is

5. Unit of Stefans constant is given by

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

7. 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

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

9. 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

10. 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,

11. The good absorber of heat are

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

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

14. 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

15. 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

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

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

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

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. Thermal equilibrium implies equality of: