Two temperature scales A and B are related by $\frac{\mathrm{A} - 42}{110} = \frac{\mathrm{B} - 72}{220}$. At which temperature two scales have the same reading ?

• − 42°

• − 72°

• + 12°

• − 40°

1.56 x 10⁵ J of heat is conducted through a 2 m² wall of 12 cm thick in 1 h. Temperature difference between the two sides of the wall is 20° C. The thermal conductivity of the material of the wall is (in W m^-1 K^-1)

• 0.11

• 0.13

• 0.15

• 1.2

In a mercury thermometer, the ice point (lower fixed point) is marked as 10° and the steam point (upper fixed point) is marked as 130°. At 40°C temperature, what will this thermometer read ?

• 78°

• 66°

• 62°

• 58°

Heat is produced at a rate given by H in a resistor when it is connected across a supply of voltage V. If now the resistance of the resistor is doubled and the supply voltage is made V/3, then the rate of production of heat in the resistor will be

• H/18

• H/9

• 6H

• 18H

245.

22320 cal of heat is supplied to 100 g of ice at O°C. If the latent heat of fusion of ice is 80 cal g^-1 and latent heat of vaporization ofwater is 540 cal g^-1, the final amount of water thus obtained and its temperature respectively are

• 8 g, 100°C

• 100 g, 90°C

• 92 g, 100°C

• 82 g, 100°C

A piece of iron is heated in a flame. If first becomes dull red then becomes reddish yellow and finally turns to white hot. The correct explanation for the above observation is possible by using

• Stefan's law

• Wien's displacement law

• Kirchoff's law

• Newton's law of cooling

The amount of heat energy required to raise the temperature of 1 g of helium at NTP, from T₁K to T₂K is

• $\frac{3}{8} {\mathrm{N}}_{\mathrm{a}}{\mathrm{K}}_{\mathrm{B}}\left({\mathrm{T}}_2 - {\mathrm{T}}_1\right)$

• $\frac{3}{2} {\mathrm{N}}_{\mathrm{a}}{\mathrm{K}}_{\mathrm{B}}\left({\mathrm{T}}_2 - {\mathrm{T}}_1\right)$

• $\frac{3}{4} {\mathrm{N}}_{\mathrm{a}}{\mathrm{K}}_{\mathrm{B}}({\mathrm{T}}_2 - {\mathrm{T}}_1)$

• $\frac{3}{4} {\mathrm{N}}_{\mathrm{a}}{\mathrm{K}}_{\mathrm{B}}\left(\frac{{\mathrm{T}}_2}{{\mathrm{T}}_1}\right)$

Same quantity of ice is filled in each of the two metal containers P and Q having the same size, shape and wall thickness but made of different materials. The containers are kept in identical surroundings. The ice in P melts completely in time t, whereas in Q takes a time t₂. The ratio of thermal conductivities of the materials of P and Q is

• t₂ : t₁

• t₁ : t₂

• t₁² : t₂²

• t₂² : t₁²

A 10 W electric heater is used to heat a container filled with 0.5 kg of water. It is found that the temperature of water and the container rises by 3°K in 15 min. The container is then emptied, dried and filled with 2 kg of oil. The same heater now raises the temperature of container-oil system by 2°K in 20 min. Assuming that there is no heat loss in the process and the specific heat of water is 4200 J kg^-1 K^-1, the specific heat of oil in the same unit is equal to

• 1.50 × 10³

• 2.55 × 10³

• 3.00 × 10³

• 5.10 × 10³

Three bodies of the same material and having masses m, m and 3m are at temperatures 40°C, 50° C and 60° C, respectively. If the bodies are brought in thermal contact, the final temperature will be

• 45°C

• 54°C

• 52°C

• 48°C