Question

A heat engine receives $150$ Joules of heat energy and performs $70$ Joules of work. If heat loss in the surrounding is zero. Find out by what value does the internal energy of the system change?

• A. $0J$
• B. $40J$
• C. $80J$
• D. $120J$
• E. $150J$

Answer 1

The correct option is C $80J$

By the first law of thermodynamics, $dQ=dU+W$

so, change in internal energy $dU=dQ-W=150-70=80J$