Physics Thermodynamics DUHS 2022
PMDC Verified Question 41 of 54
First law of thermodynamics is mathematically represented as:
A
\(\Delta U = \Delta Q - \Delta W\)
B
\(\Delta Q = \Delta W - \Delta U\)
C
\(\Delta U = \Delta W - \Delta Q\)
D
\(\Delta W = \Delta Q + \Delta U\)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: \(\Delta U = \Delta Q - \Delta W\)
1. Concept:

The First Law of Thermodynamics is the law of conservation of energy applied to thermal systems, balancing heat, internal energy, and work.

2. Formula:

$$\Delta Q = \Delta U + \Delta W$$

3. Solution:

  • The standard sign convention equation states that heat added to a system (\(\Delta Q\)) causes a change in internal energy (\(\Delta U\)) and does work on the surroundings (\(\Delta W\)).


  • Rearranging this algebraically to isolate internal energy gives: \(\Delta U = \Delta Q - \Delta W\).


4. Why other options are incorrect:

The other equations fail basic algebraic rearrangement of the First Law or imply incorrect physical phenomena (like work generating heat without changing internal energy).

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