The coefficient of performance of a refrigerator is 5. If the temperature inside freezer is -20°C, the temperature of the surroundings to which it rejects heat is  -

1. 31°C

2. 41°C

3. 11°C

4. 21°C

An ideal gas goes from state A to state B via three different processes, as indicated in the P-V diagram. If ${\mathrm{Q}}_1,$ ${\mathrm{Q}}_2,$ ${\mathrm{Q}}_3$ indicates the heat absorbed by the gas along the three processes and $∆{\mathrm{U}}_1,$ $∆{\mathrm{U}}_2,$ $∆{\mathrm{U}}_3$ indicates the change in internal energy along the three processes respectively, then:

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

(1) $∆U=-∆W,$ in a adiabatic process

(2) $∆U=∆W,$ in a isothermal process

(3) $∆U=∆W,$ in adiabatic process

(4) $∆U=-∆W,$in a isothermal process 

A monoatomic gas at pressure ${\mathrm{p}}_1$ and ${\mathrm{V}}_1$ is compressed adiabatically to $\frac{1}{8}\mathrm{th}$ its original volume. What is the final pressure of the gas ?

(1) $64 {\mathrm{p}}_1$                                   

(2) ${\mathrm{p}}_1$

(3) $16 {\mathrm{p}}_1$                                   

(4) $32 {\mathrm{p}}_1$

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

(1) 8900 J                                     

(2) 6400 J

(3) 5400 J                                     

(4) 7900 J

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) W=0                                 

(2) Q=W=0

(3) E=0                                   

(4) Q=0

In a thermodynamic process, pressure of a fixed mass of a gas is changed in such a manner that the gas molecules absorb 30 J of heat and 10 J of work is done by the gas. If the initial internal energy of the gas was 40 J, then the final internal energy will be -

(1) 30 J

(2) 20 J

(3) 60 J

(4) 40 J

If the ratio of specific heat of a gas at constant pressure to that at constant volume is γ, the change in internal energy of a mass of gas, when the volume changes from V to 2V constant pressure p, is 

(1) $R/(\gamma -1)$

(2) pV

(3) $pV/(\gamma -1)$

(4) $\gamma pV/(\gamma -1)$

If heat given to a system is 6 kcal and work done by the system is 6 kJ. Then the change in internal energy is :

(1) 19.1 kJ

(2) 12.5 kJ

(3) 25 kJ

(4) Zero

A vessel containing 5 litres of a gas at 0.8 m pressure is connected to an evacuated vessel of volume 3 litres. The resultant pressure inside will be (assuming whole system to be isolated) 

(1) 4/3 m

(2) 0.5 m

(3) 2.0 m

(4) 3/4 m