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 \(T_1\), is kept in an evacuated chamber at temperature \(T_2>T_1\). The rate of increase of temperature of the body is proportional to:
1. \(T_2-T_1\)
2. \(T^2_2 -T^2_1 \)
3. \(T^3_2 -T^3_1\) 
4. \(T^4_2 -T^4_1\)

The thermal radiation emitted by a body is proportional to \(T^n\) 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 \(10^\circ\text C\) and \(20^\circ\text C.\) The thermal radiation emitted in a given time by \(A\) and \(B\) are in the ratio of:
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. Kirchhoff'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: