Question

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​

Answer 1

C. n = P out / P in

Step-by-step 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:

`\eta = (E_(out))/(E_(in))`

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

`\eta = (P_(out))/(P_(in))`

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).