Question

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

• A. $-50J$
• B. $20J$
• C. $30J$
• D. $50J$

Answer 1

The correct option is D $50J$

Given,

$\Delta Q=+35J$

$\Delta W=-15J$

$\Delta U=?$

From law of thermodynamic,

$\Delta Q=\Delta U+\Delta W$

$\Delta U=\Delta Q-\Delta W$

$\Delta U=35-(-15)$

$\Delta U=35+15$

$\Delta U=50J$

The correct option is D.