Q117 / 200 · JIPMER 2008 · Physics

We consider a thermodynamic system. If $\Delta U$ represents the increase in its internal energy and $W$ the work done by the system, which of the following statements is true?

  • Correct answer
    A
    $\Delta U=-W$ in an adiabatic process
  • B
    $\Delta U=W$ in an isothermal process
  • C
    $\Delta U=-W$ in an isothermal process
  • D
    $\Delta U=W$ in an adiabaitc process

Solution

An isothermal process is a constant temperature process. In this process, $\begin{aligned} & T=\text { constant or } \Delta T=0 . \\ \therefore & \Delta U=n C_V \Delta T=0\end{aligned}$ An adiabatic process is defined as one with no heat transfer into or out of a system. Therefore, $Q=0$ From first law of thermodynamics $W=-\Delta U$ or $\quad \Delta U=-W$

Hence, the correct answer is option: 'A'.

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