Thermal Properties of Matter · Question 14

A black body is at a temperature of 5760 K. The energy of radiation emitted by the body at wavelength 250 nm is U1, at wavelength 500 nm is U2 and that at 1000 nm is U3. Wien's constant, b = 2.88 106 nm K. Which of the following is correct?

1. U1 > U2
2. U2 > U1
3. U1 = 0
4. U3 = 0

Two identical bodies are made of a material for which the heat capacity increases with temperature. One of these is at 100 , while the other one is at 0 . If the two bodies are brought into contact, then, assuming no heat loss, the final common temperature is

1. 50
2. more than 50
3. less than 50 but greater than 0
4. 0

A body cools from a temperature 3T to 2T in 10 minutes. The room temperature is T. Assume that Newton's law of cooling is applicable. The temperature of the body at the end of next 10 minutes will be

1. 74 T
2. 32 T
3. 43 T
4. T

The value of coefficient of volume expansion of glycerin is 5 10-4 K-1. The fractional change in the density of glycerin for a rise of 40 C in its temperature, is

1. 0.025
2. 0.010
3. 0.015
4. 0.020

The two ends of a metal rod are maintained at temperatures 100 and 110 . The rate of heat flow in the rod is found to be 4.0 J/s. If the ends are maintained at temperatures 200 and 210 , the rate of heat flow will be

1. 8.0 J/s
2. 4.0 J/s
3. 44.0 J/s
4. 16.8 J/s

On observing light from three different stars P, Q and R, it was found that intensity of violet colour is maximum in the spectrum of P, the intensity of green colour is maximum in the spectrum of R and the intensity of red colour is maximum in the spectrum of Q. If TP, TQ and TR are the respective absolute temperatures of P, Q and R, then it can be concluded from the above observations that

1. TP < TR < TQ
2. TP < TQ < TR
3. TP > TQ > TR
4. TP > TR > TQ

Steam at 100 C is passed into 20 g of water at 10 C. When water acquires a temperature of 80 C, the mass of water present will be [Take specific heat of water = 1 cal g-1 C-1 and latent heat of steam = 540 cal g-1]

1. 24 g
2. 31.5 g
3. 42.5 g
4. 22.5 g

Certain quantity of water cools from 70 C to 60 C in the first 5 minutes and to 54 C in the next 5 minutes. The temperature of the surroundings is

1. 45 C
2. 20 C
3. 42 C
4. 10 C

A piece of iron is heated in a flame. It 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

1. Kirchhoff's Law
2. Newton's Law of cooling
3. Stefan's Law
4. Wien's displacement Law

Two metal rods 1 and 2 of same lengths have same temperature difference between their ends. Their thermal conductivities are K1 and K2 and cross sectional areas A1 and A2, respectively. If the rate of heat conduction in 1 is four times that in 2, then

1. K1A1 = 4K2A2
2. K1A1 = 2K2A2
3. 4K1A1 = K2A2
4. K1A1 = K2A2