Question

First law of thermodynamics can be represented by $\Delta U=q+w$.

• A. True
• B. False

Answer 1

The correct option is A True

True. Let us consider a system whose internal energy is $U_1$. Now if we add q heat to the system the internal energy becomes $U_1+q$. Further if w work is done on the system then the final internal energy $U_2$ is given as $U_2=U_1+q+w$. Therefore the first law of thermodynamics can be represented by $\Delta U=q+w$.

Where when $q$ is positive, it is the heat added to the system.

when $q$ is negative, it is the heat taken from the system.

When w is positive, it is the work done on the system.

When $w$ is negative, it is the work done by the system.