Write the expressions for the efficiency of a full wave rectifier and a half wave rectifier.

i) Efficiency of full wave rectifier
$\mathrm{\eta }=\frac{0.812{\mathrm{R}}_{\mathrm{L}}}{{\mathrm{r}}_{\mathrm{f}}+{\mathrm{R}}_{\mathrm{L}}};{\mathrm{R}}_{\mathrm{L}}=\text{ Load resistance }$
r_f = diode forward resistance
ii) Efficiency of half wave rectifier
$\mathrm{\eta }=\frac{0.406{\mathrm{R}}_{\mathrm{L}}}{{\mathrm{r}}_{\mathrm{f}}+{\mathrm{R}}_{\mathrm{L}}}$