How does a silicon diode behave?

A silicon diode conducts in one direction only. It conducts when forward biased, turning on at about 0.7 volts, and blocks the current when reverse biased. Conventional current flows the way the triangle symbol points, from anode to cathode.

How is a diode used to protect a circuit?

A diode in series with a supply gives reverse-polarity protection: it conducts when the supply is the right way round and blocks the current if it is reversed. A diode across a relay coil or motor absorbs the voltage spike produced when the current is switched off, protecting the driving transistor.

What is half-wave rectification?

Rectification converts AC into DC. A single diode passes only the half-cycles that forward bias it and blocks the others, so the current through the load flows one way only, as a series of pulses with gaps where the opposite half-cycles are removed. A smoothing capacitor can flatten the output.

How does a Zener diode regulate a voltage?

A Zener diode is used in reverse. Once the reverse voltage reaches its Zener voltage it conducts and holds that voltage almost constant. With a series resistor from the supply, it forms a regulator: changes in the supply are dropped across the resistor while the Zener keeps the output steady, with R equal to the supply voltage minus the Zener voltage, divided by the current.

How is applications of diodes examined?

It sits in Component 1 (Discovering Electronics), a 1 hour 30 minute written paper worth 40% of the GCSE. Expect explanations and sketches of one-way conduction, reverse-polarity and spike protection, half-wave rectified output, and Zener regulation calculations for the series resistor.

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WJEC GCSE Electronics: applications of diodes overview

An overview of the applications of diodes content in Component 1 of WJEC Eduqas GCSE Electronics, covering the silicon diode's one-way behaviour, reverse-polarity and inductive-spike protection, half-wave rectification of AC to DC, and the Zener diode used with a series resistor for voltage regulation.

Generated by Claude Opus 4.86 min readWJEC Eduqas GCSE Electronics, Component 1Updated 2026-06-15

Reviewed by: AI editorial process; not yet individually human-reviewed

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How this content is examined
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For the official specification

The applications of diodes content of WJEC Eduqas GCSE Electronics is part of Component 1 (Discovering Electronics). It uses the diode's one-way behaviour for protection and for converting AC into DC, and introduces the Zener diode for voltage regulation. This page maps the content and links to a focused answer page for each part.

What the topic covers

Diodes and rectification. The silicon diode's one-way conduction (turn-on at about $0.7\,\text{V}$ ), reverse-polarity protection, inductive-spike protection across a coil, and half-wave rectification of AC to DC. See Diodes and rectification.

Zener diode voltage regulation. The Zener diode's reverse breakdown behaviour and its use with a series resistor to hold a stable, regulated output voltage. See Zener diode voltage regulation.

How this content is examined

This content sits in Component 1 (Discovering Electronics), a written paper of 1 hour 30 minutes worth 40% of the GCSE. Expect explanations and sketches of one-way conduction, protection circuits, half-wave rectified output, and Zener regulation calculations for the series resistor.

How to study it

One-way valve. A diode conducts forward (from about $0.7\,\text{V}$ ) and blocks in reverse.
Two protection roles. A series diode blocks reverse-polarity current; a coil diode absorbs the switch-off spike.
Sketch rectified output. Half-wave gives positive humps with flat gaps, not smooth DC.
Zener in reverse. The Zener holds the output at its Zener voltage once in breakdown.
Size the series resistor. Use $R = \dfrac{V_{\text{supply}} - V_Z}{I}$ and check the power.

For the official specification

WJEC Eduqas publishes the full GCSE Electronics specification, past papers and mark schemes at wjec.co.uk. Always revise from the current specification and the board's own past papers, because question style and the printed equation and symbol lists are board-specific.

Sources & how we know this

WJEC Eduqas GCSE Electronics specification (from 2017) — WJEC Eduqas (2017)