The circuit diagram below is a simple current rectifier circuit. Use it to answer the questions that follow: (a) State the function of each of the parts lab...

Answer Details

The circuit shown is a simple half-wave rectifier with a smoothing (filter) stage. An a.c. supply feeds a diode, which passes current in one direction only, and the output is then smoothed before it reaches the load.

(a) Functions of the labelled parts

• A - This is the a.c. source (the secondary winding of the transformer). Its function is to supply the alternating current (a.c.) that is to be rectified.
• B - This is the smoothing (reservoir) capacitor connected across the load. Its function is to smoothen the rectified current. It charges up near the peak of each pulse and then discharges slowly through the load during the gaps, so it fills in the dips and greatly reduces the ripple, giving an almost steady d.c. output.

(b) Sketch of the output signal

Before smoothing, the rectifier delivers a series of separate voltage pulses (broken line). After the capacitor B is added, these pulses are smoothed into a nearly steady d.c. voltage that carries only a small saw-tooth ripple (solid line). The output is therefore unidirectional (one-way) and almost constant, as sketched below.

Thus the final output is a steady, one-directional (d.c.) voltage with a small ripple, rather than the alternating voltage supplied by A.