Question 27 (3 points)
if p equals an amount of energy, which equation correctly expresses n, or energy
efficiency?
a. n=p out + p in
b. n- pout - pin
c. n = p out / p in

C. n = P out / P in

Explanation:

Efficiency, in terms of energy, is generally defined as the amount of useful energy in output from a system divided by the amount of energy in input needed to make the system working.

Mathematically:

Or, since in our problem the energy is labelled with P,

No machine can have an efficiency of 1.0 (100 %), because not all the energy in input can be converted into useful output energy: part of it, in fact, is wasted because of internal frictions, and converted into thermal energy (heat).

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