Question

Which of the following is the mathematical form of first law of thermodynamics?

• A. $\Delta U=W$ for an adiabatic process
• B. $\Delta U=q$ for an isochoric process
• C. $q=-W$ for an isothermal process
• D. All of the above

Answer 1

The correct option is D All of the above

According to first law of thermodynamics,
$\Delta U=q+W$
Where, $\Delta U=\text{change in internal energy}$
$q=\text{amount of heat absorbed or released}$
$W=\text{work done by the system or on the system}$

For an adiabatic process $q=0$
$\Delta U=w$

For an isochoric process $W=P\Delta V=P\times 0=0$
$\therefore \Delta U=q$
For an isothermal process
$\Delta U=0\text{and so}q=-w$
Hence all are correct.