Which equation represents the efficiency of an a.c. generator?
- A$\dfrac{\text{electrical energy output}}{\text{total energy input}}$
- B$\dfrac{\text{electrical energy output}}{\text{thermal energy output}}$
- C$\dfrac{\text{total energy output}}{\text{electrical energy input}}$
- D$\dfrac{\text{thermal energy output}}{\text{total energy input}}$