Thermal Properties of Matter

A wire of length 10 cm and diameter 0.5 mm is used in a bulb. The temperature of the wire is 1727 and power radiated by the wire is 94.2 W. Its emissivity is x8 where x = . (Given = 6.0 10-8 W m-2 K-4, = 3.14 and assume that the emissivity of wire material is same at all wavelengths.)

Two cylindrical rods A and B made of different materials, are joined in a straight line. The ratios of lengths, radii and thermal conductivities of these rods are: LALB = 12, rArB = 2 and KAKB = 12. The free ends of rods A and B are maintained at 400 K, 200 K, respectively. The temperature of rods interface is K, when equilibrium is established.

Consider a rectangular sheet of solid material of length l = 9 cm and width d = 4 cm. The coefficient of linear expansion is = 3.1 10-5 K-1 at room temperature and one atmospheric pressure. The mass of sheet m = 0.1 kg and the specific heat capacity Cv = 900 J kg-1 K-1. If the amount of heat supplied to the material is 8.1 102 J then change in area of the rectangular sheet is :

1. 2.0 10-6 m2
2. 6.0 10-7 m2
3. 3.0 10-7 m2
4. 4.0 10-7 m2

Pressure of an ideal gas, contained in a closed vessel, is increased by 0.4\% when heated by 1 . Its initial temperature must be:

1. 2500 K
2. 25
3. 250
4. 250 K

Match List - I with List - II. Choose the correct answer from the options given below :

1. (A)-(IV), (B)-(III), (C)-(II), (D)-(I)
2. (A)-(III), (B)-(I), (C)-(II), (D)-(IV)
3. (A)-(III), (B)-(IV), (C)-(I), (D)-(II)
4. (A)-(II), (B)-(III), (C)-(I), (D)-(IV)

The difference of temperature in a material can convert heat energy into electrical energy. To harvest the heat energy, the material should have

1. low thermal conductivity and high electrical conductivity
2. low thermal conductivity and low electrical conductivity
3. high thermal conductivity and high electrical conductivity
4. high thermal conductivity and low electrical conductivity

A cup of coffee cools from 90 to 80 in t minutes when the room temperature is 20 . The time taken by the similar cup of coffee to cool from 80 to 60 at the same room temperature is:

1. 135t
2. 1013t
3. 513t
4. 1310t

The temperature of a body in air falls from 40 to 24 in 4 minutes. The temperature of the air is 16 . The temperature of the body in the next 4 minutes will be :

1. 283
2. 563
3. 423
4. 143

Which of the following figure represents the relation between Celsius and Fahrenheit temperatures?

1. [figure]
2. [figure]
3. [figure]
4. [figure]

A gun fires a lead bullet of temperature 300 K into a wooden block. The bullet having melting temperature of 600 K penetrates into the block and melts down. If the total heat required for the process is 625 J, then the mass of the bullet is grams. (Latent heat of fusion of lead =2.5 104 J Kg-1 and specific heat capacity of lead =125 J Kg-1 K-1)

1. 20
2. 15
3. 5
4. 10