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1.

Find the efficiency of a cycle consisting of two isochoric and two adiabatic lines if the volume of the ideal gas changes `n=10` times within the cycle. The working gas has `gamma=1.5`.

Answer» Correct Answer - `0.68`
Discussion
2.

In a mechanical refrigerator the low -temperature coils are at a temperature of `-13^(@)C` and the compressed gas in the condenser at a temperature `27^(@)C`. What is the theoretical coefficient of performance.

Answer» Correct Answer - `6.5`
Discussion
3.

In a two stage heat engine a quantity of heat `Q_(1)` is absorbed at a temperature `T` work `W_(1)` is done and a quantity of heat `Q_(2)` expelled at a lower temperature `T_(2)` by the first state. The second state absorbs the heat expelld by the first, does work `W_(2)` and expels a quanity of heat `Q_(3)` at a lower temperature `T_(2)` Calculate the effiency of the combination engine.

Answer» Correct Answer - `1-(T_(3))/(T_(1))`
Discussion
4.

A brass rod is in thermal contact with a heat reservoir at `127^(@)C` at one end and a heat reservoir at `27^(@)C` at the other end. Find the total change in entropy arising from the process of conduction of 1200 cal of heat through the rod. Does the entropy of the rod change?

Answer» Correct Answer - `1cal K^(-1)`
Discussion
5.

In a specific heat experiment `100g` of lead (sp. Heat`=145Jkg^(-1)K^(-1)`) at `100^(@)C` is mixed with `200g` of water at `20^(@)`. Find the change in entropy.

Answer» Correct Answer - `0.574Jkg^(-1)`
Discussion
6.

Calculate the efficiency of a cycle consisting of two isobaric and two adiabtic lines, if the pressure changes `n=10` times within the cycle. The working substances is an ideal gas of adiabatic exponent `gamma=1.5`.

Answer» Correct Answer - `0.53`
Discussion
7.

The heat capacity of a refrigerating chamber is `80000cal`. Calculate the time in which the temperature of the chamber is reduced from `0.5^(@)C` ot `0^(@)C` if the power of the motor working the machine is `300W`. Ambient temperature `=27^(@)C`.

Answer» Correct Answer - `55s`
Discussion
8.

The entropy of `v = 4.0` moles of an ideal gas increases by `Delta S = 23 J//K` due to the isothermal expansion. How many times should the volume `v = 4.0` moles of the gas be increased ?

Answer» Correct Answer - 2
Discussion