Consider a compound slab consisting of two different materials having an equal thickness and thermal conductivities K and 2K respectively. The equivalent thermal conductivity of the slab is :
1.
2. 3K
3. K
4. K
The coefficient of thermal conductivity of copper is nine times that of steel in the composite cylindrical bar shown in the figure. What will be the temperature at the junction of copper and steel?
1. C
2. C
3. C
4. C
A slab consists of two parallel layers of two different materials of the same thickness having thermal conductivities and . The equivalent conductivity of the combination is :
1.
2.
3.
4.
A black body has a maximum wavelength at temperature 2000 K. Its corresponding wavelength at temperature 3000 k will be :
1.
2.
3.
4.
Assuming the sun to be a spherical body of radius R at a temperature of T K, evaluate the total radiant power, incident on Earth, at a distance r from the Sun :
1.
2.
3.
4.
Two identical metal balls at temperature C and C kept in the air at C. The ratio of net heat loss by these bodies is :
1. 1/4
2. 1/2
3. 1/16
A calorimeter of mass 0.2 kg and specific heat 900 J/kg-K is containing 0.5 kg of a liquid of specific heat 2400 J/kg-K. Its temperature falls from C to C in one minute. The rate of cooling is :
1. 5 J/s
2. 15 J/s
3. 100 J/s
4. 115 J/s
A hot liquid is filled in a container and kept in a room of temperature of C. The liquid emits heat at the rate of 200 when its temperature is C. When the temperature of the liquid becomes C, the rate of heat loss in is :
1. 160
2. 140
3. 80
4. 60
Three rods made of the same material and having the same cross section have been joined as shown in the figure. Each rod is of the same length. The left and right ends of the combination are kept at C and C respectively. The temperature of the junction of the three rods will be :
1. C
2. C
3. C
4. C
Ice starts forming in the lake with water at C and when the atmospheric temperature is C. If the time taken for 1 cm of ice be 7 hours, then the time taken for the thickness of ice to change from 1 cm to 2 cm is :
1. 7 hours
2. 14 hours
3. Less than 7 hours
4. More than 7 hours
The figure shows a system of two concentric spheres of radii and and kept at temperatures and , respectively. The radial rate of flow of heat in a substance between the two concentric spheres is proportional to :
1.
2.
3.
4. In
Three rods of the same dimensions are arranged as shown in the figure. They have thermal conductivities , and. The points P and Q are maintained at different temperatures for the heat to flow at the same rate along PRQ and PQ, then which of the following options is correct?
1.
2.
3.
4.
The plots of intensity versus wavelength for three black bodies at temperatures , and respectively are as shown. Their temperatures are such that :
1.
2.
3.
4.
Which of the following graphs correctly represents the relation between and where E is the amount of radiation emitted per unit time from unit area of a body and T is the absolute temperature?
1.
2.
3.
4.
A liquid in a beaker has a temperature (t) at time t and is the temperature of surroundings, then according to Newton's law of cooling, the correct graph between and t is :
1.
2.
3.
4.