Question

A gas in an insulated cylinder with a movable piston is compressed adiabatically and 100J of work is done in the process. The gas is then allowed to expand adiabatically while doing 10J of work. What is the net change in internal energy?

Answer 1

For adiabatic process $\delta Q=0$ and $\delta W=-dU$ . So, $\Delta U=100-10=90\ (J)$