The circuit diagram of a full wave rectifies: A centre tap transformer and two identical divides $D_1$ and $D_2$ are used to diagram a full wave rectifies. The centre-tap transformer has 3 output terminals. Centre tap is $C$ is always at $\text{OV}$.Drawing positive half cycle of $\text{AC}, A$ is +ve and $B$ is $-v e$. For negative half cycle, B is + ve and A is - ve. So, when positive half cycle appears, A is +ve, B is $-v e$ and $c$ is $O$.So, divide $D_1$ is forward biased and divide $D_2$ is reverse biased.When negative half cycle appears,$A$ is -ve, $B$ is + Ve and $C$ is $O$So, divide $D_2$ is forward biased and divide $D_1$ is reverse biased.So, for each half cycle one divide conducts current through $R_{L}$ flows unidirectionally. Hence the voltage developed across $R_L$ is a DC.