Heat and Thermodynamics

1

If θi is the inversion temperature, θn is the neutral temperature, θc is the temperature of the cold junction, then

  1. θi - θc = 2θn
  2. θc - θi = 2θn
  3. θi + θc = θn
  4. θn = (θi + θc)/2
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2

Even Carnot engine cannot give 100% efficiency because we cannot

  1. eliminate friction
  2. reach absolute zero temperature
  3. prevent radiation
  4. find ideal sources
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3

Three rods of Copper, Brass and Steel are welded together to from a Y-shaped structure. Area of cross-section of each rod = 4 cm2. End of copper rod is maintained at 100°C where as ends of brass and steel are kept at 0°C.

Lengths of the copper, brass and steel rods are 46, 13 and 12 cm respectively. The rods are thermally insulated from surroundings except at ends. Thermal conductivities of copper, brass and steel are 0.92, 0.26 and 0.12 CGS units respectively. Rate of heat flow through copper rod is:

  1. 6.0 cal/s
  2. 4.8 cal/s
  3. 2.4 cal/s
  4. 1.2 cal/s
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4

Heat given to a body which raises its temperature by 1°C is

  1. specific heat
  2. thermal capacity
  3. temperature gradient
  4. water equivalent
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5

Two spheres of the same material have radii 1 m and 4 m and temperatures 4000 K and 2000 K respectively. The ratio of the energy radiated per second by the first sphere to that by the second is

  1. 1:1
  2. 1:9
  3. 16:1
  4. 4:1
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6

1 mole of a gas with γ = 7/5 is mixed with 1 mole of a gas with γ = 5/3, then the value of γ for the resulting mixture is

  1. 2/5
  2. 24/16
  3. 12/7
  4. 7/5
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7

Cooking gas containers are kept in a lorry moving with uniform speed. The temperature of the gas molecules inside will

  1. decrease for some, while increase for others
  2. decrease
  3. increase
  4. remain same
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