In summer, a mild wind is often found on the shore of a calm river. This is caused due to:
a. the difference in thermal conductivity of water and soil.
b. convection currents.
c. conduction between air and the soil.
d. radiation from the soil.
Choose the correct option:
1. (a) , (b) 
2. (b)  only
3. (d) only 
4. (a) , (d) 

A piece of charcoal and a piece of shining steel of the same surface area are kept for a long time on an open lawn in the bright sun.
a. The steel will absorb more heat than the charcoal.
b. The temperature of the steel will be higher than that of the charcoal.
c. If both are picked up by bare hands, the steel will be felt hotter than the charcoal.
d. If the two are picked up from the lawn and kept in a cold chamber, the charcoal will lose heat at a faster rate than the steel.
Choose the correct option:
1.  (a), (b) 
2.  (c), (d) 
3.  (d) only 
4.  (a), (d) 

A heated body emits radiation which has maximum intensity near the frequency v₀ . The emissivity of the material is 0.5. If the absolute temperature of the body is doubled.

(a) the maximum intensity of radiation will be near the frequency 2v₀ 

(b) the maximum intensity of radiation will be near the frequency v₀ /2

(c) the total energy emitted will increase by a factor of 16

(d) the total energy emitted will increase by a factor of 8

Choose the correct option 

1.  (a) , (c) 

2. (b) , (c) 

3.  (d) only 

4. (a) , (d) 

A solid sphere and a hollow sphere of the same material and of equal radii are heated to the same temperature.

(a) Both will emit equal amount of radiation per unit time in the biginning.

(b) Both will absorb equal amount of radiation from the surrounding in the biginning.

(c) The initial rate of cooling (dT/dt) will be the same for the two spheres.

(d) The two spheres will have equal temperatures at any instant

Choose the correct option 

1.  (a) , (b) 

2. (b) , (c) 

3.  (d) only 

4. (a) , (d) 

A blackbody does not: 
a. emit radiation.
b. absorb radiation.
c. reflect radiation.
d. refract radiation.
Choose the correct option:
1. (a), (b) 
2. (b), (c) 
3. (c), (d) 
4. (a), (d) 

One end of a metal rod is dipped in boiling water and the other is dipped in melting ice.

(a) All parts of the rod are in thermal equilibrium with each other.

(b) We can assign a temperature to the rod.

(c) We can assign a temperature to the rod after steady state is reached.

(d) The state of the rod does not change after steady state is reached

Choose the correct option 

1.  (a) , (b) 

2. (b) , (c) 

3.  (d) only 

4. (a) , (d) 

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:

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.

            
1. a

2. b

3. c

4. d

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.