Thermal Properties of Matter

The coefficient of performance of a refrigerator is 5. If the temperature inside freezer is -20^o C, th temperature of the surroundings to which it rejects heat is

• 31^o C

• 41^o C

• 11^o C

• 11^o C

The value of the coefficient of volume expansion of glycerin is 5 x 10^-4 K^-1. The fractional change in the density of glycerin for a rise of 40⁰C in its temperature is 

• 0.015

• 0.020

• 0.025

• 0.025

A cylindrical metallic rod in thermal contact with two reservoirs of heat at its two ends conducts an amount of heat Q in time t. The metallic rod is melted and the material is formed into a rod of half the radius of the original rod. What is the amount of heat conducted by the new rod when placed in thermal contact with the two reservoirs in time t?

• Q/4

• Q/16

• 2Q

• 2Q

If C_p- C_v denote the specific heats (per unit mass) of an ideal gas of molecular weight M
Here R is the molar gas constant

• C_p-C_V = R/M²

• C_p-C_V = R

• C_p-C_V = R/M

• C_p-C_V = R/M

A block body t 227^o C radiates heat at the rate of 7 cal cm^-2 s^-1. At  a temperature of 727^o C, the rate of heat radiated in the same units will be 

• 60

• 50

• 112

• 112

On a new scale of temperature (which is linear), an called the W scale, the freezing and boiling point of water are 39^o W and 239^o W respectively. what will be the temperature of 39^o C  celsius scale?

• 78^o W

• 117^o C

• 200^o C

• 200^o C

An electric kettle takes 4 A current at 220 V. How much time will it take to boil 1 kg of water from temperature 20⁰ C? The temperature boiling water is 100^o C^.

• 6.3 min

• 8.4 min

• 12.6 min

• 12.6 min

If the cold junction of a thermocouple is kept at 0^o C and the hot junction is kept at T^o C, then the relation between neutral temperature (T_n) and temperature of inversion (T_i) is:

• 

• T_n = 2T_i

• T_n = T_i -T

• T_n = T_i -T

Nickel shows the ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature, then it will show:

• paramagnetism

• anti -ferromagnetism

• no magnetic property

• no magnetic property

A black body is at 727^o C. It emits energy at a rate which is proportional to:

• (727)²

• (1000)⁴

• (1000)²

• (1000)²