CCEA GCSE Physics 2.3 Electricity Exam Questions

About CCEA GCSE Physics 2.3 Electricity

Electricity is a major Unit 2 topic in CCEA GCSE Physics with two prescribed practicals: the voltage-current graph for a metal wire and how resistance depends on the length of a wire. You need to draw circuits using standard symbols, use Q = It and V = IR, explain how the resistance of a filament lamp changes, and calculate total resistance in series and parallel. The topic also covers electrical power and energy, the kilowatt-hour and the cost of using appliances, two-way switching, and the safety features of a three-pin plug. It links to magnetism and transformers in 2.4. Examiners often set multi-step circuit calculations and fuse choice questions.

What you need to know

• Current and charge Current is the flow of electrons; conventional current flows from positive to negative, opposite to electron flow. Charge = current x time, Q = It, with charge in coulombs (C).
• Ohm's law and the wire practical For a metal wire at constant temperature, V = IR and current is directly proportional to voltage, giving a straight line through the origin on a V-I graph. Use an ammeter in series and a voltmeter in parallel, and keep the current low to avoid heating.
• Filament lamp and resistance factors As current through a filament lamp increases, it gets hotter and its resistance increases, so the graph curves. Resistance of a wire increases with length (prescribed practical), decreases with greater cross-sectional area and depends on the material.
• Series and parallel circuits In series the current is the same everywhere and total resistance R = R1 + R2. In parallel the voltage across each branch is the same, branch currents add up, and 1/R = 1/R1 + 1/R2, so the total is less than the smallest resistor.
• Power, energy and cost Power = current x voltage, P = IV. Energy = power x time. Units used = power (kW) x time (h) in kilowatt-hours; cost = units x price per unit.
• Plugs and safety Live wire is brown, neutral is blue and earth is green and yellow. The fuse is in the live wire and melts if the current is too high. The earth wire protects users of metal-cased appliances; double insulated appliances do not need one. Choose the fuse rating just above the normal current (3 A, 5 A or 13 A).

Common mistakes in 2.3 Electricity

• Connecting a voltmeter in series. It must be in parallel across the component.
• Forgetting to convert minutes to seconds in Q = It or W to kW in cost calculations.
• Adding parallel resistances directly. Use 1/R = 1/R1 + 1/R2 and remember to invert at the end.
• Choosing a fuse rating below the normal working current. The fuse would blow in normal use.
• Saying the earth wire stops you getting a shock by blowing. The earth wire provides a low resistance path so a large current flows and the fuse melts.

Try three 2.3 Electricity exam-style questions