The thermal conductivity of a rod depends on
1. length
2. mass
3. area of cross section
4. material of the rod.
In a room containing air, heat can go from one place to another:
1. by conduction only
2. by convection only
3. by radiation only
4. by all three modes
A solid at temperature T1, is kept in an evacuated chamber at temperature T2 > T1 . The rate of increase of temperature of the body is proportional to
1. T2 – T1
2. \(T^2_2 -T^2_1\)n
3. \(T^3_2 -T^3_1\)
4. \(T^4_2 -T^4_1\)
The thermal radiation emitted by a body is proportional to Tn where T is its absolute temperature. The value of n is exactly 4 for
1. a blackbody
2. all bodies
3. bodies painted black only
4. polished bodies only.
Two bodies A and B having equal surface areas are maintained at temperatures 10°C and 20°C. The thermal radiation emitted in a given time by A and B are in the ratio
1. 1 : 1.15
2. 1 : 2
3. 1 : 4
4. 1 : 16.
One end of a metal rod is kept in a furnace. In steady state, the temperature of the rod
1. increases
2. decreases
3. remains constant
4. is nonuniform
Newton’s law of cooling is a special case of
1. Wien’s displacement law
2. Kirchoff 's law
3. Stefan’s law
4. Planck’s law.
1. a
2. b
3. c
4. d
A hot liquid is kept in a big room. The logarithm of the numerical value of the temperature difference between the liquid and the room is plotted against time. The plot will be very nearly
1. a straight line
2. a circular arc
3. a parabola
4. an ellipse.
A body cools down from \(65^\circ \text{C}\) to \(60^\circ \text{C}\) in \(5\) minutes. It will cool down from \(60^\circ \text{C}\) to \(55^\circ \text{C}\) in:
1. | \(5\) minutes |
2. | less than \(5\) minutes |
3. | more than \(5\) minutes |
4. | less than or more than \(5\) minutes depending on whether its mass is more than or less than \(1\) kg |