Thermal Properties of Matter · Question 39

Consider a compound slab consisting of two different materials having equal thicknesses and thermal conductivities K and 2K, respectively. The equivalent thermal conductivity of the slab is

1. 23K
2. 2K
3. 3K
4. 43K

Unit of Stefan's constant is

1. watt m2 K4
2. watt m2/K4
3. watt/m2 K
4. watt/m2K4

Consider two rods of same length and different specific heats (S1, S2), conductivities (K1, K2) and area of cross-sections (A1, A2) and both having temperatures T1 and T2 at their ends. If rate of loss of heat due to conduction is equal, then

1. K1A1 = K2A2
2. K1A1S1 = K2A2S2
3. K2A1 = K1A2
4. K2A1S2 = K1A2S1

For a black body at temperature 727 , its radiating power is 60 watt and temperature of surrounding is 227 . If temperature of black body is changed to 1227 then its radiating power will be

1. 304 W
2. 320 W
3. 240 W
4. 120 W

Which of the following is closest to an ideal black body?

1. lamp black
2. cavity maintained at constant temperature
3. platinum black
4. a lump of charcoal heated to high temperature.

The Wien's displacement law expresses relation between

1. wavelength corresponding to maximum energy and temperature
2. radiation energy and wavelength
3. temperature and wavelength
4. colour of light and temperature.

A cylindrical rod has temperatures T1 and T2 at its ends. The rate of flow of heat is Q1 cal/s. If all the linear dimensions are doubled keeping the temperatures constant, then the rate of flow of heat Q2 will be

1. 4Q1
2. 2Q1
3. Q14
4. Q12

Gravitational force is required for

1. stirring of liquid
2. convection
3. conduction
4. radiation

A black body emits maximum energy at wavelength m at 2000 K. Its corresponding wavelength at 3000 K will be

1. 32 m
2. 23 m
3. 1681 m
4. 8116 m