CAPE Physics Unit 2 · 2007 · Paper 1 · Question Q6

A cell of internal resistance r is connected to a load of resistance R. The efficiency of such an arrangement is found from the expression \frac{\text{energy dissipated in the load}}{\text{energy dissipated in the complete circuit}} Which expression represents the efficiency in this case?

1. (A)\frac{r}{R+r}
2. (B)\frac{r}{R}
3. (C)\frac{R}{R+r}
4. (D)\frac{R}{r}