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Difficulty: MediumDiodes

In a basic electronic power supply circuit, an alternating current (AC) voltage source is connected in series with a standard semiconductor diode and a load resistor. Which of the following describes the electrical behavior of this circuit across a complete AC cycle?

  1. A
    It permits current to flow freely in both directions while stepping down the alternating voltage to a lower amplitude.
  2. B
    It stores electrical energy in an electrostatic field during the positive half-cycle and discharges it into the load during the negative half-cycle.
  3. It conducts current only during the positive half-cycle when forward-biased, blocking current during the negative half-cycle to produce pulsating direct current.Answer
  4. D
    It inverts the polarity of the negative half-cycle to convert the alternating waveform into continuous, perfectly smooth direct current.

Answer

The diode conducts current only during the positive half-cycle when forward-biased, blocking current during the negative half-cycle to produce pulsating direct current.
A semiconductor diode operates as a one-way electrical valve. During the positive half-cycle of an applied AC signal, the diode is forward-biased and conducts current through the load resistor. During the negative half-cycle, the diode is reverse-biased and blocks current flow. This action converts bidirectional AC into unidirectional pulsating DC through half-wave rectification.

Step-by-Step Solution

1
Analyze the diode biasing state during the positive half-cycle of the AC input voltage.
The anode becomes positive with respect to the cathode, placing the PN junction in forward bias.
Forward bias narrows the depletion region and allows current to pass through the diode and into the load resistor.
2
Analyze the diode biasing state during the negative half-cycle of the AC input voltage.
The anode becomes negative with respect to the cathode, placing the PN junction in reverse bias.
Reverse bias widens the depletion region, preventing current flow through the circuit during this half-cycle.
3
Determine the net output current and voltage waveform across the load resistor.
Current flows through the load only during the positive half-cycles in a single direction, resulting in pulsating direct current (DC).
This conversion of alternating current to pulsating direct current using a single diode is the foundation of half-wave rectification.

Key Concept

Half-wave rectification and unidirectional conduction of semiconductor diodes
Estimated Time:1m 0s
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