Rectifiers and Power Supplies: Half-Wave, Full-Wave, and Bridge Quiz Quiz

Explore the fundamentals of rectifiers and power supply circuits with questions focusing on half-wave, full-wave, and bridge rectifiers. Assess your ability to identify key features, operation principles, and practical uses of these essential electronic components.

1. Half-Wave Rectifier Output

   Which statement best describes the output waveform of a half-wave rectifier when a sinusoidal AC voltage is applied?

   1. Only the positive half-cycles of the AC input appear at the output.
   2. The output is a steady DC voltage with zero ripple.
   3. The output switches polarity every cycle.
   4. Both positive and negative half-cycles appear at the output.

   Explanation: A half-wave rectifier allows only the positive half-cycles of the AC input to pass through, blocking the negative half-cycles entirely. As a result, the output consists solely of positive pulses with gaps in between. Both positive and negative half-cycles appearing at the output is incorrect, as this describes an unrectified AC waveform. A steady DC with zero ripple is not possible due to the pulsating nature of the output, and switching polarity every cycle is not characteristic of any typical rectifier.

2. Full-Wave Rectifier Advantage

   Why does a full-wave rectifier provide a smoother DC output than a half-wave rectifier given the same input and filter?

   1. It uses twice as many diodes, which regulate the voltage.
   2. It blocks both halves of the AC input, reducing output current.
   3. It inverts the negative half to form a triangular waveform.
   4. It rectifies both halves of the AC waveform, doubling the output frequency.

   Explanation: A full-wave rectifier inverts the negative half of the AC input so both halves contribute to the output, effectively doubling the frequency of the rectified signal. This increased ripple frequency is easier to filter, leading to smoother DC. Using more diodes does not itself smooth the output; regulation is not the main mechanism here. Blocking both halves would result in no output current, and forming a triangular waveform does not describe the rectification process.

3. Bridge Rectifier Diode Configuration

   Given a bridge rectifier circuit, how many diodes conduct during each half-cycle of the AC input?

   1. Three diodes conduct alternatively.
   2. Two diodes conduct in each half-cycle.
   3. Only one diode conducts per half-cycle.
   4. All four diodes conduct at once.

   Explanation: In a bridge rectifier, two diodes conduct during each half-cycle to direct current in the same direction across the load. All four diodes conducting is incorrect as it would short the supply. Only one diode conducting is characteristic of a half-wave rectifier, not a bridge. Three diodes never conduct simultaneously in this configuration.

4. Peak Inverse Voltage (PIV) in Rectifiers

   For a given secondary voltage, which rectifier configuration requires diodes with the highest Peak Inverse Voltage (PIV) rating?

   1. Half-wave rectifier
   2. Bridge rectifier
   3. Series-rectifier circuit
   4. Full-wave center-tapped rectifier

   Explanation: A full-wave center-tapped rectifier requires each diode to withstand the entire secondary voltage across itself during non-conduction, resulting in the highest PIV requirement among the options. In a half-wave circuit, the PIV requirement is lower. A bridge rectifier has a lower PIV per diode than the center-tapped version. A series-rectifier circuit is not a standard rectifier type and is not relevant here.

5. Importance of Filter Capacitors

   Why are filter capacitors commonly used after rectifiers in power supply circuits?

   1. They lower the rectified voltage to zero.
   2. They change the output waveform to square form.
   3. They increase the AC component (ripple) of the output.
   4. They store energy and provide a smoother DC output by reducing ripple.

   Explanation: Filter capacitors store charge during voltage peaks and release energy when the rectified voltage drops, filling gaps and making the DC output smoother by reducing ripple. Increasing ripple or producing a square waveform is incorrect, as capacitors do not serve those functions in this context. Lowering the rectified voltage to zero is not a purpose of filter capacitors.