- The flow of heat from a hot body to a cold body is an example of
- Isothermal process
- Reversible process
- Adiabatic process
- Irreversible process

Three black bodies A, B and C in the form of cubes of sides in the ratio of 3: 4: 5 are kept at the same high temperature. The ratio of the quantity of heat lost per second by A, B and C will be- 27: 64: 125
- 5: 4: 3
- 9: 16: 25
- 25: 16: 9

A sphere, a cube and a thin circular plate all made of the same material and having the same mass are initially heated to a temperature of 300°C. which one of these cools faster?- Circular plate
- Sphere
- Cube
- All will cool at the same rate

- The emissive of a perfectly black body is
- 0
- 0.5
- 1
- 0.75

- If the wavelengths of maximum intensity of radiation emitted by the moon and the sun are 10
^{–4}m and 0.5 × 10^{–6}m respectively, then the ratio of their temperature is- 200
- 100

The coefficient of transmission of a perfectly black body is- Zero
- One
- 0.5
- 0.75

When a black body is heated, it emits heat radiations of- Infrared wavelengths
- Ultraviolet wavelengths
- All wavelengths
- A particular wavelengths

An ideal black body is represented by- A metal coated with a black dye
- A glass surface coated with coal tar
- A hollow enclosure blackened from inside and having a small hole
- A lump of charcoal heated to a high temperature

The temperature of a furnace is 2327°C and the intensity is maximum in its radiation spectrum at 1200. If the intensity in the spectrum of a star is maximum at 4800, then the surface temperature of the star is- 6500 K
- 6000 K
- 4800 K
- 7500 K

The coefficient of transmission and coefficient of reflection for a given body at a given temperature are 0.33 and 0.64 respectively. Then the coefficient of emission of the same body at the same temperature will be- 0.3
- 0.003
- 0.03
- 0.33

- The correct equation out of the following is

The maximum wavelength of radiation emitted by a black body at 1227°C is λm. What is its maximum wavelength at 2227°C?

According to Prevost’s theory of heat exchange, the heat exchange shops at- 0°C
- – 5°C
- – 273°C
- – 273 K

- The rate of cooling of a body is 0.5°C/minute, when the body is 50°C above the surrounding. What is the rate of cooling if the body is 30°C above the surrounding?
- 24°C/hour
- 18°C/hour
- 30°C/hour
- 12°C/hour

Coefficient of transmission and coefficient of reflection for a given body are 0.22 and 0.74 respectively. Then, at a given temperature, the coefficient of emission for the body is- 0.4
- 0.04
- 0.96
- 0.22

If a black body is heated from 27°C to 927°C, then the ratio of the radiation emitted by the body at the two temperatures will be- 1: 4
- 1: 16
- 1: 256
- 1: 64

- A body cools from 100°C to 70°C in 8 minutes. If the room temperature is 15°C and assuming Newton’s law of cooling holds good, then time required for the body to cool from 70°C to 40°C is
- 14 s
- 10 s
- 8 s
- 5 s

A body radiates heat at the rate of 4 cal/m^{2}/s, when its temperature is 227°C. what is the heat radiated by the same body when its temperature is 727°C?- 8 cal/m
^{2}/s - 16 cal/m
^{2}/s - 64 cal/m
^{2}/s - 32 cal/m
^{2}/s

- 8 cal/m

Two thermometers A and B exposed to sunlight. The value of A is painted black but that of B is not painted. The correct statement regarding this case is- Temperature of B will rise faster
- Temperature of A will remain more than B
- Both of A and B show equal rise from the beginning
- Temperature of A will rise faster than B but the final temperature will be same in both

Two spheres made of same material have radii in the ratio 2: 1. if both the spheres are at same temperature, then what is the ratio of heat radiation energy emitted per second by them?- 1: 4
- 4: 1
- 3: 4
- 4: 3

The temperature of a black body is gradually increased. The colour of the body will change from- White-green-red
- Red-yellow-blue
- Red-violet-yellow
- Yellow-green-red

Radiation emitted by a surface is directly proportional to- Third power of its temperature
- Equal to its temperature
- Twice power of its temperature
- Fourth power of its temperature

The coefficient of absorption of perfectly black body is- 1
- 0
- 0.75
- None of these

Two bodies A and B at temperatures T_{1}K and T_{2}K respectively have the same dimensions. Their emissivities are in the ratio of 1: 3. if they radiate the same amount of heat per unit time, then the relation between their temperatures is given by

A body radiates heat at the ate of 5 cal/m^{2}-s when its temperature is 227°C. the heat radiated by the same body when its temperature is 727°C is- 10 cal/m
^{2}-s - 20 cal/m
^{2}-s - 40 cal/m
^{2}-s - 80 cal/m
^{2}-s

- 10 cal/m