Question

What is the change in internal energy of a system if \(500\,\text{J}\) of heat is added and \(200\,\text{J}\) of work is done by the system?

• A. \(300\,\text{J}\)
• B. \(700\,\text{J}\)
• C. \(200\,\text{J}\)
• D. \(500\,\text{J}\)

Hint:

In thermodynamics sign convention: Heat added to the system is positive, and work done by the system is subtracted.

Answer 1

The Correct Option is A

Concept: According to the First Law of Thermodynamics, \[ \Delta U = Q - W \] where \(Q\) = heat added to the system, \(W\) = work done by the system.

Step 1: Substitute the given values. \[ Q = 500\,\text{J}, \quad W = 200\,\text{J} \] \[ \Delta U = 500 - 200 \]

Step 2: Calculate the change in internal energy. \[ \Delta U = 300\,\text{J} \]