Conduction Law

Q.

The dimensions of the coefficient of thermal conductivity are

1. 

2. 

3. 

4. 

Q. A cylindrical aluminium rod of length 2m is maintained at a temperature difference of 10${}^{\circ }$ Celsius. The radius of the rod is 1 cm. Will it make a difference if the temperature difference was 10 Kelvin instead?

1. Yes
2. No

Q. Ice starts forming in lake with water at $0^{\circ }$ C and when the atmospheric temperature is $-{10}^{\circ }$ 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. More than 7 hours
4. Less than 7 hours

Q. Two vessels of different materials are similar in size in every respect. The same quantity of ice filled in them gets melted in 20 minutes and 40 minutes respectively. The ratio of thermal conductivities of the materials is

1. 5 : 6
2. 2 : 1
3. 6 : 5
4. 3 : 1

Q.

An ice box used for keeping eatable cold has a total wall area of $1metr{e}^2$ and a wall thickness of 5.0 cm. The thermal conductivity of the ice box is $K=0.01joule/metre{-}^{\circ }C$. It is filled with ice at $0^{\circ }$ along with eatables on a day when the temperature is ${30}^{\circ }$. The latent heat of fusion of ice is $334\times {10}^{3}joules/kg$ . The amount of ice melted in one day is
(1 day =86, 400 seconds )

1. 776 gms
2. 7760 gms
3. 1552 gms
4. 11520 gms

Q.

Choose the correct statements(s) from the following:

1. A temperature change which increases the length of a steel rod by 0.1% will increase its volume by nearly 0.3%

2. The specific heat of a solid is different when the solid is heat at (a) constant pressure and (b) the constant volume

3. The thermal conductivity of air being less than for wool, we prefer wool to air for thermal insulation.

4. When the distance between two fixed points is measured with a steel tape, the observed reading will be less on a hot day than on a cold day.

Q.

A slab of stone of area $0.34m^2$ and thickness 10 cm is exposed on the lower face to steam at ${100}^{\circ }C$. A block of ice at $0^{\circ }C$ rests on the upper face of the slab. In one hour, 3.6 kg of ice is melted. Assume that the heat loss from the sides is negligible. The latent heat of fusion of ice is $3.4\times {10}^{4}Jk{g}^{-1}$. What is the thermal conductivity of the stone in units of $J{s}^{-1}{m}^{-1}{C}^{-1}$?

1. 1.5

2. 2.0

3. 2.5

4. 1.0

Q.

Five rods of same dimensions are arranged as shown in the figure. They have thermal conductivities $K_1,K_2,K_3,K_{4}and{K}_5$. When points A and B are maintained at different temperatures, no heat flows through the central rod if

1. 
2. 
   
3. 
4. 

Q. 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 are kept at $0^{\circ }$ C and ${90}^{\circ }$ C respectively. The temperature of the junction of the three rods will be

1. 
2. 
3. 
4. 

Q.

What is the SI unit of the coefficient of thermal conductivity?

1. 

2. 

3. 

4.