Thermodynamics (Physics) · Question 41

If and represent the increase in internal energy and work done by the system respectively in a thermodynamical process, which of the following is true?

1. = - , in an adiabatic process
2. = , in an isothermal process
3. = , in an adiabatic process
4. = - , in an isothermal process

The internal energy change in a system that has absorbed 2 kcal of heat and done 500 J of work is

1. 6400 J
2. 5400 J
3. 7900 J
4. 8900 J

In thermodynamic processes which of the following statements is not true ?

1. In an isochoric process pressure remains constant.
2. In an isothermal process the temperature remains constant.
3. In an adiabatic process PV = constant.
4. In an adiabatic process the system is insulated from the surroundings.

If Q, E and W denote respectively the heat added, change in internal energy and the work done in a closed cyclic process, then

1. E = 0
2. Q = 0
3. W = 0
4. Q = W = 0

An engine has an efficiency of 1/6. When the temperature of sink is reduced by 62 , its efficiency is doubled. Temperatures of the source is

1. 37
2. 62
3. 99
4. 124

A Carnot engine whose sink is at 300 K has an efficiency of 40%. By how much should the temperature of source be increased so as to increase its efficiency by 50% of original efficiency?

1. 380 K
2. 275 K
3. 325 K
4. 250 K

The molar specific heat at constant pressure of an ideal gas is (7/2) R. The ratio of specific heat at constant pressure to that at constant volume is

1. 9/7
2. 7/5
3. 8/7
4. 5/7

An ideal gas heat engine operates in Carnot cycle between 227 and 127 . It absorbs 6 104 cal of heat at higher temperature. Amount of heat converted to work is

1. 4.8 104 cal
2. 6 104 cal
3. 2.4 104 cal
4. 1.2 104 cal

Which of the following processes is reversible?

1. Transfer of heat by conduction
2. Transfer of heat by radiation
3. Isothermal compression
4. Electrical heating of a nichrome wire

One mole of an ideal gas at an initial temperature of T K does 6R joule of work adiabatically. If the ratio of specific heats of this gas at constant pressure and at constant volume is 5/3, the final temperature of gas will be

1. (T + 2.4) K
2. (T - 2.4) K
3. (T + 4) K
4. (T - 4) K