12.8 An electric heater supplies heat to a system at a rate of 100W. If system performs work at a rate of 75 joules per second. At what rate is the internal energy increasing?
12.8 An electric heater supplies heat to a system at a rate of 100W. If system performs work at a rate of 75 joules per second. At what rate is the internal energy increasing?
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1 Answer
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Heat is supplied to the system at a rate of 100W
Hence, heat supplied, Q = 100 J/s
The system performs at the rate of 75 J/s
Hence, work done, W = 75 J/s
From the 1st law of Thermodynamics, we have Q = U + W, where U is the internal energy
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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