Chapter 15, Problem 1FC

To determine

What positive value of Q and positive value of W represents in the first law of thermodynamics.

Answer to Problem 1FC

Positive value of Q represents the (c) system gains heat and positive value of W represents the work is done by the system.

Explanation of Solution

The expression of the first law of thermodynamics is,

$\begin{array}{c}\Delta U=U_f-U_i\\ =Q-W\end{array}$

Whenever the system gains the heat, the value of Q is positive. Similarly, the value of Q is negative whenever the system loses the heat.

If the work is done by the system, the value of W is positive. Similarly, the value of W is negative when the work is done on the system.

Conclusion:

Hence, the positive value of Q represents the (c) system gains heat and positive value of W represents the work is done by the system.