MCQ
An electric heater supplies heat to a system at a rate of $100\;W.$ If system performs work at a rate of $75$ Joules per second. At what rate (in $J/s$) is the internal energy increasing?
- A$36$
- B$20$
- C$30$
- ✓$25$
✓
Answer
Correct option: D.
$25$
d
Heat is supplied to the system at a rate of $100 W$
Heat is supplied to the system at a rate of $100 W$
Heat supplied, $Q=100 J / s$
The system performs at a rate of $75 J / s$
Work done, $W=75 J / s$
From the first law of thermodynamics, we have
$Q=U+W$
Where, $U=$ Internal energy
$\therefore U= Q -W$
$=100-75$
$=25 J / s$
$=25 W$
Therefore, the internal energy of the given electric heater increases at a rate of $25\; W$
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