Free Rectification MCQs with Answers

1. Rectification is the process of converting

• A. direct current to alternating current
• B. alternating current to direct current
• C. low voltage to high voltage
• D. current to voltage

Explanation: A diode conducts in one direction only, so it can strip out one half of the alternating cycle and leave a unidirectional output. Converting direct to alternating current is inversion, done by an inverter, which is the opposite process. Every mains powered electronic device contains a rectifier of some kind.

2. In a half wave rectifier, the output

• A. uses both halves of the input cycle
• B. consists of one half cycle only, with the other half missing
• C. is a steady direct voltage
• D. is zero

Explanation: The single diode conducts only while its anode is positive, so alternate half cycles are blocked and the output is a series of pulses with gaps between them. This makes it inefficient and hard to smooth, since the ripple frequency is only that of the supply. A full wave rectifier inverts the other half instead of discarding it.

3. A full wave bridge rectifier uses

• A. one diode
• B. two diodes
• C. four diodes
• D. no diodes

Explanation: Four diodes arranged in a bridge route both halves of the cycle through the load in the same direction, so the output has twice the pulse frequency of a half wave circuit and is far easier to smooth. Its advantage over the two diode centre tap arrangement is that it needs no centre tapped transformer. Two of the four diodes conduct during each half cycle.

4. A capacitor connected across the output of a rectifier acts as

• A. an amplifier
• B. a smoothing element, charging at the peaks and discharging between them to reduce ripple
• C. a switch
• D. an oscillator

Explanation: The capacitor stores charge while the rectified voltage rises and releases it while the voltage falls, filling in the troughs so the output approaches a steady direct voltage. A larger capacitance or a larger load resistance gives less ripple, since the time constant is longer. Full wave rectification smooths better than half wave because the gaps to be filled are shorter.

5. The ripple frequency at the output of a full wave rectifier fed from a 50 Hz supply is

• A. 25 Hz
• B. 50 Hz
• C. 100 Hz
• D. 200 Hz

Explanation: Both halves of each cycle produce an output pulse, so there are two pulses per input cycle and the ripple appears at twice the supply frequency. A half wave rectifier would give ripple at 50 Hz instead. The higher ripple frequency is one reason full wave output is easier to smooth.