O-Level Physics Electricity & Magnetism Practical Manual (Paper 3)

2 | Planning responses examiners reward

1. Aim & theory - reference Ohm’s law, $F = B I L$, or Faraday’s law to show you know the governing relationship for the setup (items 16–18 in the 2026 syllabus).
2. Variables - state independent variables (applied voltage, current, coil speed) and dependent variables (current, magnetic deflection, induced emf); control factors such as wire length, core material, and coil geometry.
3. Method - explain wiring steps, polarity checks, and repeat readings at regular intervals (e.g. increasing voltage in $\pu{0.5 V}$ steps).
4. Safety - limit current to avoid overheating, switch off power before reconfiguring circuits, and keep magnets away from electronics.
5. Data treatment - describe plotting $V$ vs $I$ (gradient $= R$), torque vs current, or induced emf vs speed; include how you will calculate gradients and interpret polarity reversals.

3 | MMO discipline for circuit-heavy tasks

• Component checks: Inspect wires, ensure crocodile clips bite clean metal, and confirm meters return to zero before starting.
• Meter configuration: Connect voltmeters in parallel and ammeters in series; select ranges that keep readings in the upper half of the scale for better precision.
• Power supply use: Start with low voltage, increase gradually, and note supply internal resistance when discussing discrepancies.
• Magnetic setups: Position compasses away from bench clutter, tap gently to overcome friction, and align coils with protractors for consistent angle readings.
• Induction runs: Move magnets swiftly and consistently; for rotating coils, keep angular speed steady and record peak deflections for both directions to evidence polarity change.

4 | PDO & ACE moves to secure full credit

• Tabulate raw readings with units and processed values (e.g. $I$, $V$, $V/I$, induced voltage).
• Plot straight-line graphs when possible: $V$ vs $I$ (slope $= R$) or induced emf vs frequency/speed.
• Quote uncertainties for current and voltage (meter least counts), discuss heating effects or internal resistance as systematic errors, and suggest improvements like using a rheostat or allowing components to cool.
• For magnetic effect tasks, tie observations to field patterns and discuss how increasing coil turns strengthens the field.
• In induction discussions, explicitly reference Faraday's law: explain how greater rate of change of flux leads to larger induced emf; mention that reversing motion reverses polarity.
• Document data-logger advantages (higher sampling rate, reduced reaction-time error) if data-loggers are used - the syllabus notes candidates are expected to be familiar with data-loggers, and Planning may include their appropriate use.

5 | Practice prompts before the practical window

1. Three-resistor audit: Build series and parallel networks, record $I$-$V$ sets, and compare measured resistance with theoretical values; write an ACE paragraph on why heating skews results.
2. Current-balance drill: Suspend a conductor in a magnetic field, vary current, and record force or deflection angle; plot force vs current and explain intercepts or offsets.
3. Induction sweeps: Move a bar magnet through a coil at different speeds, record galvanometer peaks, and explain how doubling speed affects the induced emf magnitude and sign.

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Sources

1. SEAB, GCE O-Level Physics (6091) Syllabus 2026 - scheme of assessment and apparatus list

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