What equations are needed for WJEC GCSE Electronics circuit concepts?

The key equations are the charge equation Q equals I times t, Ohm's law V equals I times R, the power equations P equals V times I and P equals I squared times R, and the energy equation E equals P times t. These are printed in the specification, but you must select the right one and substitute with the correct units, converting milliamps to amps and minutes to seconds.

What are the I-V characteristics you must know?

Three: an ohmic resistor gives a straight line through the origin (constant resistance); a filament lamp gives an S-shaped curve that bends over as it heats up and its resistance rises; a silicon diode conducts one way only, blocking the reverse current and turning on at about 0.7 volts in the forward direction.

What are the series and parallel circuit rules?

In series the current is the same everywhere and the supply voltage is shared so the parts add to the supply. In parallel each branch has the full supply voltage and the current splits, so the branch currents add to the supply current. Current is conserved at a junction: what flows in flows out.

What test equipment is examined in circuit concepts?

A multimeter measures current, voltage and resistance on selected ranges; an ammeter (in series) measures current and a voltmeter (in parallel) measures voltage; an oscilloscope displays how a voltage changes with time so you can read its amplitude and period; a logic probe shows whether a digital point is logic high, low or pulsing.

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WJEC GCSE Electronics: circuit concepts overview

Q: How is circuit concepts examined?

It sits in Component 1 (Discovering Electronics), a 1 hour 30 minute written paper worth 40% of the GCSE. Expect calculations with the charge, Ohm's law, power and energy equations, sketching and explaining I-V graphs, series and parallel circuit analysis, choosing test equipment, and reading or completing circuit diagrams from the standard symbols.

An overview of the circuit concepts content in Component 1 of WJEC Eduqas GCSE Electronics, covering charge, current and voltage, resistance and Ohm's law, the I-V characteristics of a resistor, lamp and diode, the power and energy equations, the series and parallel rules, circuit symbols and test equipment.

Generated by Claude Opus 4.87 min readWJEC Eduqas GCSE Electronics, Component 1Updated 2026-06-15

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

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What the topic covers
How this content is examined
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For the official specification

The circuit concepts content of WJEC Eduqas GCSE Electronics gives you the quantities, equations and rules that every later topic depends on. It is part of Component 1 (Discovering Electronics). This page maps the content and links to a focused answer page for each part.

What the topic covers

Charge, current and voltage: Charge in coulombs, current as the rate of flow of charge with $Q = It$ , voltage as energy per unit charge, the standard circuit symbols, and the test equipment (multimeter, oscilloscope, logic probe). See Charge, current and voltage.
Resistance and Ohm's law: Resistance, $V = IR$ , and the I-V characteristics of an ohmic resistor, a filament lamp and a silicon diode. See Resistance and Ohm's law.
Power and energy: The power equations $P = VI$ and $P = I^2R$ , the energy equation $E = Pt$ , and choosing a suitable power rating. See Power and energy.
Current and voltage rules: The series and parallel rules: current conserved at junctions, voltages adding around a loop. See Current and voltage rules.

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 calculations with the charge, Ohm's law, power and energy equations, sketching and explaining I-V graphs, analysing series and parallel circuits, choosing the right test instrument, and reading or completing circuit diagrams from the standard symbols.

How to study it

Drill the equations. Practise $Q = It$ , $V = IR$ , $P = VI$ , $P = I^2R$ and $E = Pt$ until choosing and rearranging them is automatic.
Convert units first. Milliamps to amps, minutes to seconds, before substituting.
Learn the three I-V graphs. Straight line (resistor), S-curve (lamp), one-way step at $0.7\,\text{V}$ (diode), with the reason for each shape.
Know the rules. Series shares voltage with one current; parallel gives each branch the full voltage and splits the current.
Match the instrument to the job. Ammeter in series, voltmeter in parallel, oscilloscope for a changing voltage, logic probe for a digital state.

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)