Electricity is a core part of GCSE Physics. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
CurrentRate of flow of charge, measured in amperes.
Potential differenceEnergy transferred per unit charge, measured in volts.
ResistanceOpposition to current; V = IR (Ohm's law).
Series circuitsOne path; current is the same throughout.
Parallel circuitsMultiple paths; pd is the same across each branch.
Electrical powerP = VI; the rate of energy transfer.
PowerP = V I = I^2 R = V^2 / R
EnergyE = P t = V I t
Series add RR = R1 + R2
Parallel add 1/R1/R = 1/R1 + 1/R2
ChargeQ = I t
Joule = watt second1 J = 1 W s
Ohmic conductorStraight line through origin
Filament bulbCurve - R rises with T
Common mistakes to avoid
Questions where students often pick the tempting wrong answer — make sure you know the right one:
What happens to the total resistance when you add another resistor in parallel?✗ Adding any resistor always increases the total resistance. ✓ Total resistance decreases — there are more paths for current to flow.
What happens to the current as it goes around a series circuit?✗ Current gets used up by each component as it flows around the circuit. ✓ It stays the same at every point — current is conserved.
What does voltage (potential difference) across a component represent?✗ Voltage is the 'amount of electricity' flowing through the wire. ✓ The energy transferred per unit charge passing through that component.
The I-V graph of a filament lamp is a curve that flattens out. Why?✗ The diode blocks reverse current ✓ Its resistance increases as it heats up
Which instrument measures current, and how is it connected?✗ Voltmeter, in parallel ✓ Ammeter, in series
Practise Electricity — free games
Test yourself with these quick revision games for this topic:
See all 17 games in the Subjects Arcade →
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