If the amount of heat given to a system is 35 J and the amount of work done on the system is 15 J, then the change in internal energy of the system is

Options

A. `-50 J`
B. 20J
C. `-20 J`
D. 50 J

Answer

D

Explanation

According to first law of thermodynamics
`delta Q = Delta U + Delta W` or `Delta U = Delta Q - Delta W`
here , `Delta Q = 35 J, Delta W = -15 J :. Delta U = 35 J - (-15 J) = 50 J`
Note : `Delta W` is negative because work done on the system.