What kind of work does a machine with an efficiency of 40% do if the amount of heat 20 KJ is supplied from the heater?

Given: η (efficiency of the used machine) = 40% (0.4); Q (heat supplied from the heater) = 20 kJ.

We express the work that the machine used should have done from the formula: η = Ap / Q, whence Ap = Q * η.

Let’s make a calculation: Ap = 20 * 0.4 = 8 kJ.

Answer: The machine used had to do a work of 8 kJ.




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