Question

Which of the following is the correct equation?

• A. ?U = ?W + ?Q
• B. ?U = ?Q - W
• C. ?W = ?U + ?Q
• D. None of these

Answer 1

Answer: (A)

?U = ?W + ?Q

Answer 2

$\Delta U =\Delta Q + W$
This is the mathematical relation of the first law of thermodynamics.
Here,
$\Delta U =$ change in internal energy;
$\Delta Q =$ heat absorbed by the system and
$W =$ work done by the system.