Physics Thermodynamics ETEA 2023
PMDC Verified Question 23 of 54
In a certain process, 200J of heat energy is supplied to a system and the same time 50 J of work is done by the system. The increase in the internal energy of the system is:
A
150 J
B
250 J
C
25 J
D
100 J
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: 150 J
1. Concept:

The First Law of Thermodynamics tracks energy conservation. Net energy stored in the system is the energy added minus the energy expelled as work.

2. Formula:

$$\Delta U = Q - W$$

3. Solution:

  • Given heat supplied to the system, \(Q = +200 \text{ J}\).


  • Given work done by the system, \(W = +50 \text{ J}\).


  • Substitute into the First Law: \(\Delta U = 200 - 50\).


  • The resulting increase in internal energy is \(150 \text{ J}\).


4. Why other options are incorrect:

Adding 200 and 50 yields 250J (incorrectly assuming work was done ON the system). Other answers result from arbitrary division or ignoring the work completely.

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