Edexcel International GCSE Physics Section 6: Magnetism and Electromagnetism Exam Questions

About Edexcel International GCSE Physics Section 6: Magnetism and Electromagnetism

Section 6 of Edexcel International GCSE Physics covers magnets, the magnetic effects of currents and electromagnetic induction. You start with magnetic and non-magnetic materials, induced magnetism and field patterns, including the uniform field between opposite poles. Electromagnetism covers the fields around wires and coils, electromagnets, and the force on a current-carrying conductor in a magnetic field, used in motors and loudspeakers. Electromagnetic induction then explains generators, the factors affecting induced voltage and how transformers change voltage. It links to Section 2 on electricity and Section 4 on generating electricity. Examiners like field diagrams, Fleming's left-hand rule questions and transformer calculations.

What you need to know

• Magnetic materials Iron, steel, nickel and cobalt are magnetic. Soft magnetic materials (iron) are easily magnetised and demagnetised, suitable for electromagnets; hard materials (steel) keep their magnetism.
• Field patterns Field lines run from north to south. Plot fields using a compass or iron filings. A uniform field between opposite poles has parallel, evenly spaced lines.
• Currents and fields A current in a wire produces a circular field around it. A coil (solenoid) produces a field like a bar magnet; adding an iron core makes a strong electromagnet.
• Motor effect A current-carrying wire in a magnetic field experiences a force. Its direction is given by Fleming's left-hand rule. The force increases with a larger current or stronger field, and reverses if either is reversed.
• Motors and loudspeakers In a d.c. motor, forces on the coil create a turning effect, increased by more current, more turns or a stronger field. A loudspeaker uses varying current in a coil to make a cone vibrate.
• Electromagnetic induction A voltage is induced when a conductor moves through a magnetic field or the field through a coil changes. It increases with faster movement, stronger field and more turns.
• Transformers Alternating current in the primary coil creates a changing magnetic field in the iron core, inducing an alternating voltage in the secondary. Vp / Vs = np / ns and, for 100% efficiency, Vp Ip = Vs Is. High voltage transmission reduces current and energy loss in cables.

Common mistakes in Section 6: Magnetism and Electromagnetism

• Saying aluminium or copper are magnetic. They are not magnetic materials.
• Using the right hand for the motor effect. Use Fleming's left-hand rule for the force on a current-carrying conductor.
• Saying a transformer works on d.c. It needs an alternating current to produce a changing field.
• Saying a voltage is induced when the magnet is stationary inside a coil. There must be relative movement or a changing field.
• Thinking a step-up transformer increases power. It increases voltage but reduces current; power cannot increase.

Try three Section 6: Magnetism and Electromagnetism exam-style questions