If ΔQ and ΔW represent the heat supplied to the system and  the work done on the system, respectively, then the first law of thermodynamics can be written as: (where ΔU is the internal energy)
1. ΔQ = ΔU + ΔW
2. ΔQ = ΔU – ΔW
3. ΔQ = ΔW – ΔU
4. ΔQ = –ΔU – ΔW

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

Can two isothermal curves cut each other?

An ideal gas A and a real gas B have their volumes increased from V to 2 V under isothermal conditions. The increase in internal energy 

(1) Will be same in both A and B

(2) Will be zero in both the gases

(3) Of B will be more than that of A

(4) Of A will be more than that of B

The latent heat of vaporisation of water is \(2240~\text{J/gm}\). If the work done in the process of expansion of \(1~\text{g}\) is \(168~\text{J}\), then the increase in internal energy is:
1. \(2408~\text{J}\)
2. \(2240~\text{J}\)
3. \(2072~\text{J}\)
4. \(1904~\text{J}\)

An ideal gas at \(27^{\circ}\mathrm{C}\) is compressed adiabatically to $\frac{8}{27}$ of its original volume. If $\gamma =\frac{5}{3}$, then the rise in temperature will be:
1. 450 K
2. 375 K
3. 225 K
4. 405 K

If $\gamma$ denotes the ratio of two specific heats of a gas, the ratio of slopes of adiabatic and isothermal PV curves at their point of intersection is 

(1) $\frac{1}{\gamma }$

(2) $\gamma$

(3) $\gamma -1$

(4) $\gamma +1$

Air in a cylinder is suddenly compressed by a piston, which is then maintained at the same position. With the passage of time 

(1) The pressure decreases

(2) The pressure increases

(3) The pressure remains the same

(4) The pressure may increase or decrease depending upon the nature of the gas

A polyatomic gas \(\left(\gamma = \frac{4}{3}\right)\) is compressed to \(\frac{1}{8}\) of its volume adiabatically. If its initial pressure is \(P_0,\) its new pressure will be:

For adiabatic processes $\left(\gamma =\frac{C_p}{C_v}\right)$ 

(1) $P^{\gamma }V$ = constant

(2) $T^{\gamma }V$ = constant

(3) $T{V}^{\gamma -1}$ = constant

(4) $T{V}^{\gamma }$ = constant