In order to produce steady d.c. from the ‘bumpy’ d.c. that results from rectification, a smoothing capacitor must be incorporated in the circuit, in parallel with the load resistor R
the capacitor charges up and maintains the voltage at a high level. It discharges gradually
when the rectified voltage drops, but the voltage soon rises again and the capacitor charges up again. The result is an output voltage with ‘ripple’.
A large capacitor discharges more slowly than a small capacitor, so will give less ripple. Similarly, if R has a large value, C will discharge more slowly. In practice, the greater the value of the quantity R × C, the smoother the rectified a.c. However, if R and C have large values, it will be difficult to change the value of the voltage quickly.
