CBSE
Multiple Choice Questions1.56 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
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
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
A solid maintained at t1° C is kept in an evacuated chamber at temperature t2° C (t2 >>t1). The rate of heat absorbed by the body is proportional to
t24 − t14
(t24 + 273) − (t14 + 273)
t2 − t1
t22 − t12
