A wire is stretched under a force. If the wire suddenly snaps the temperature of the wire

• remains the same

• decrease

• increase

• first decrease then increase

When the room temperature becomes equal to the dew point, the relative humidity of the room is

• 100 %

• zero %

• 70 %

• 85 %

Two rods of equal length and diameter have thermal conductivities 3 and 4 units respectively. If they are joined in series, the thermal conductivity of the combination would be

• 3.43

• 3.5

• 3.4

• 3.34

234.

19 g of water at 30°C and 5 g of ice at -20°C are mixed together in a calorimeter. What is the final temperature of the mixture ? (Given specific heat of ice = 0.5 cal g^-1 (C)^-1 and latent heat of fusion of ice = 80 cal g^-1)

• 0°C

• − 5°C

• 5°C

• 10°C

It is difficult to cook rice in an open vessel by boiling it at high altitudes because of

• low boiling point and high pressure

• high boiling point and low pressure

• low boiling point and low pressure

• high boiling point and high pressure

The height of a waterfall is 50 m. If g = 9.8 ms^-2 the difference between the temperature at the top and the bottom of the waterfall is

• 1.17°C

• 2.17°C

• 0.117°C

• 1.43°C

Experimental investigations show that the intensity of solar radiation is maximum for a wavelength 480 nm in the visible region. Estimate the surface temperature of sun. (Given Wien's constant b = 2.88 x 10^-3 mK.)

• 4000 K

• 6000 K

• 8000 K

• 10⁶ K

The temperature of an ideal gas is increased from 120 K to 480 K. If at 120 K, the root mean square speed of gas molecules is v, then at 480 K, it will be

• 4v

• 2v

• $\frac{\mathrm{v}}{2}$

• $\frac{\mathrm{v}}{4}$

A block of ice at temperature -20°C is slowly heated and converted to steam at 100°C. Which of the following diagram is most appropriate ?

Two black bodies at temperatures 327°C and  427°C are kept in an evacuated chamber at 27°C. The ratio of their rates of loss of heat are

• $\frac{6}{7}$

• ${\left(\frac{6}{7}\right)}^2$

• ${\left(\frac{6}{7}\right)}^3$

• $\frac{243}{464}$