Question

Based on the first law of thermodynamics, which one of the following is correct?

• A. For an adiabatic process : $\Delta E = -q$
• B. For an isochoric process, $E = - Q$
• C. For a isothermal process : $ E = -Q$
• D. For a cyclic process, $W = -Q$

Answer 1

Answer: (D)

First law of Thermodynamics is

$\Delta E=Q+W$

(a) For isochoric process, $\Delta V=0$

$w=p \Delta V=0$

$\therefore \Delta E=Q$

(b) For adiabatic process, $Q=0$

$\Delta E=W$

(c) For isothermal process, $\Delta T=0$ and

$\Delta E=0 $

$Q=-W$

(d) For cyclic process, state functions like

$\Delta E=0$

$Q=-W$