At GCSE
At GCSE you use V = IR, P = IV, and the rules for series and parallel circuits. Household electricity (live/neutral/earth, fuses, the National Grid) and I-V characteristics of fixed resistors, filament lamps and diodes appear every series.
GCSEA-LevelAQAEdexcelOCR
Electricity revision — GCSE & A-Level Physics
Electricity questions reward fluent use of V = IR, P = IV and the rules for series and parallel circuits. At GCSE you also need the household electricity section (mains, fuses, earthing) and the National Grid.
At A-Level the topic extends into emf, internal resistance, potential dividers and Kirchhoff's laws. Required practicals on I-V characteristics and resistivity are reliable mark earners.
At A-Level
At A-Level you add emf and internal resistance (ε = I(R + r)), potential dividers, Kirchhoff's laws and the resistivity of a wire (required practical). Questions on power dissipation in real circuits and the behaviour of thermistors and LDRs are common.
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Example flashcards
Q: State Ohm's law as an equation.
A: V = IR (potential difference = current × resistance), valid for an ohmic conductor at constant temperature.
Q: What happens to the total resistance when more resistors are added in parallel?
A: It decreases — more paths are available for current to flow.
Q: Calculate the power dissipated by a 12 Ω resistor carrying 2 A.
A: P = I²R = 4 × 12 = 48 W.
Q: Define emf.
A: The energy transferred per unit charge by a source (e.g. a battery) — measured in volts.
Quick summary
Electricity is a high-yield Physics topic for GCSE and A-Level students (AQA, Edexcel, OCR). At A-Level you add emf and internal resistance (ε = I(R + r)), potential dividers, Kirchhoff's laws and the resistivity of a wire (required practical). Examiners reward precise definitions and applied explanations — focus on the core ideas and the small set of terms that come up every series.
Key terms
- Current
- Potential difference
- Resistance
- Ohm's law
- Series circuit
- Parallel circuit
- Power
- EMF
- Internal resistance
Electricity FAQs
Why does the resistance of a filament bulb increase with current?+
More current heats the filament; higher temperature means more lattice vibrations, so electrons collide more often and resistance rises. Filament bulbs are non-ohmic.
Why are domestic appliances connected in parallel?+
Each device gets the full mains voltage, can be switched on or off independently and a fault in one does not break the circuit.
What is the difference between AC and DC?+
Direct current flows in one direction (e.g. from a battery). Alternating current reverses direction periodically; UK mains is 50 Hz AC at 230 V.
Why is high voltage used in the National Grid?+
For a given power, higher voltage means lower current, so less energy is lost as heat in the transmission cables (P_loss = I²R).
Related Physics topics
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