Physics Exam — Circuits, Ohm's Law, Current and Magnetism
Master the three electrical quantities (voltage, current and resistance), Ohm's law (V = I × R), series and parallel circuits, the difference between direct and alternating current, conductors and insulators, magnetism, electromagnets and electrical power.
Electricity is everywhere —your phone, the fridge, the light in your room— but we rarely stop to understand what it actually is: charges moving through a circuit, governed by a relationship as simple as it is powerful, Ohm's law. It is one of those topics where the gap between memorising and truly understanding really shows.
The exam covers the three electrical quantities (voltage, current and resistance) and Ohm's law (V = I × R), the difference between series and parallel circuits, conductors and insulators, direct and alternating current, and the basics of electromagnetism: how a current generates a magnetic field and how that drives motors and maglev trains.
Apply Ohm's law and revise circuits with the exam below, with the working explained step by step.
Physics & Chemistry · Primary & Secondary
V = I × R. Knowing any two quantities gives you the third. A 10 Ω resistor at 5 V draws 0.5 A. This single formula unlocks most circuit problems at secondary level.
Series: same current through all components — one failure stops the circuit. Parallel: same voltage across each branch — one failure leaves the rest running. Household wiring is always parallel.
A wire carrying current generates a magnetic field. Electromagnets (coil + iron core + current) are the heart of electric motors, MRI scanners, maglev trains and hard drives.
"A Year 8 student wonders why Christmas lights all go out when one bulb fails. The exam explains series circuits — and why modern LED strings use parallel wiring instead."
Tricks and techniques to master this topic faster:
Ohm's law triangle: cover the quantity you want (V, I or R) — the remaining two show the formula.
AC vs DC: batteries give DC; the mains socket gives AC (230 V, 50 Hz in Europe).
Good conductors: copper, silver, aluminium. Good insulators: plastic, rubber, glass, dry wood.
Power formula: P = V × I. A 230 V, 0.26 A bulb consumes ≈ 60 W.
If you are studying Electricity and Magnetism, these curriculum topics complement each other:
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