MCQ
A system is provided with $200$ cal of heat and the work done by the system on the surroundings is $40J.$ Then, its internal energy:
- AIncreases by $600J.$
- BDecreases by $800J.$
- ✓Increases by $800J.$
- DDecreases by $50J.$
✓
Answer
Correct option: C.
Increases by $800J.$
Given, $\text{dQ = +200cal}$
$= 200 \times 4.2$
$= 840\text{J, dW}$
$= +40J$
From first law of thermodynamics,
$\text{dQ = dW + dW}$
$\text{dU = dQ - dW}$
$= 840 - 40$
$= 800J.$
$= 200 \times 4.2$
$= 840\text{J, dW}$
$= +40J$
From first law of thermodynamics,
$\text{dQ = dW + dW}$
$\text{dU = dQ - dW}$
$= 840 - 40$
$= 800J.$
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