Diodes are used in electrical power supply circuits primarily as

• A. rectifiers
• B. relays
• C. switches
• D. transistors

Answer: (A)

Diodes in electrical power supply circuits are used primarily to convert alternating current into direct current. A diode conducts current in only one direction, so when fed with AC it passes the positive half-cycle and blocks the negative, producing a pulsating DC. A bridge rectifier uses four diodes to convert both halves of the AC waveform into pulsating DC, which is then smoothed by capacitors to produce a steadier DC output. This rectification step is the essential function of diodes in most power supplies. Other devices like relays are mechanical switches; diodes are not used as switches. Transistors act as active switching or regulation elements, whereas the diode’s job is to provide a unidirectional current path for rectification, though diodes can assist regulation in some designs.