GCSE Physics: Waves & Electromagnetism — Revision Workbook

Inside GCSE Physics: Waves & Electromagnetism — Revision Workbook

tell transverse from longitudinal waves and label amplitude, wavelength, frequency and period (T = 1 ÷ f), calculate wave speed with v = fλ and place the electromagnetic spectrum in order with its uses and dangers, sort permanent from induced magnets and read magnetic field lines, then master the motor effect F = BIl, Fleming’s left-hand rule and the d.c. motor before an exam-style task. About 30 minutes.

Learning objectives

• wave properties — transverse versus longitudinal waves, and amplitude, wavelength, frequency and period, including T = 1 ÷ f;
• wave speed and behaviour — the equation v = fλ used to find speed and frequency, and reflection and refraction;
• the electromagnetic spectrum — the order radio, micro, infrared, visible, ultraviolet, X-ray and gamma, with everyday uses and dangers;
• magnets and magnetic fields — permanent versus induced magnets, field lines, the magnetic effect of a current, solenoids and electromagnets;
• the motor effect — F = BIl, Fleming’s left-hand rule, the simple d.c. motor and the idea of transformers and generators.

Activities in this book

1. Task 1 — Wave Properties

   in a transverse wave the vibrations are at 90° (perpendicular) to the direction of energy transfer — like ripples on water or light. In a longitudinal wave the vibrations are parallel to the energy transfer, making compressions and rarefactions — like sound. Learn the four properties: amplitude, wavelength, frequency and period, and the link T = 1 ÷ f.

2. Task 2 — Wave Speed & the EM Spectrum

   the wave-speed equation is v = fλ (speed = frequency × wavelength), where v is in m/s, f in Hz and λ in m. Reflection is a wave bouncing off a surface (an echo); refraction is a wave changing direction as it speeds up or slows down entering a new material. The electromagnetic spectrum runs radio, micro, infrared, visible, ultraviolet, X-ray, gamma — longest wavelength to shortest.

3. Task 3 — Magnets & Magnetic Fields

   a permanent magnet produces its own magnetic field all the time; an induced magnet becomes magnetic only in a magnetic field and loses most of its magnetism when removed. Field lines always run from the north pole to the south pole, and are closest together where the field is strongest. A current in a wire makes a magnetic field — wind the wire into a solenoid, add an iron core, and you have a switchable electromagnet.

4. Task 4 — The Motor Effect & Beyond

   when a current-carrying wire sits in a magnetic field, the field and the current interact to push the wire — the motor effect. The force is F = BIl (force = magnetic flux density × current × length). Fleming’s left-hand rule gives its direction: First finger = Field, seCond finger = Current, thuMb = Motion (force). A split-ring commutator keeps a d.c. motor spinning; a transformer changes the voltage of an a.c. supply by electromagnetic induction.

5. Task 5 — Exam-Style Application

   exam questions reward joined-up physics: state the equation, substitute the numbers with units, and explain the physics behind a device. For a 6-mark question, plan three or four clear points, use the correct key terms, and answer every part.

Suggestions for teaching

• Start with a diagram. Label amplitude, wavelength and rest position on a transverse wave, and compressions and rarefactions on a longitudinal one, before any calculations.
• Drill v = fλ. Cover speed = frequency × wavelength, rearrange for f = v ÷ λ, and always check the units (m/s, Hz, m).
• Chant the EM spectrum. Radio, micro, infrared, visible, ultraviolet, X-ray, gamma — longest wavelength to shortest — then match each to a use and a danger.
• Model Fleming’s left-hand rule. First finger = Field, seCond finger = Current, thuMb = Motion; practise it with F = BIl calculations.
• Link to real devices. Tie the motor effect to the d.c. motor and induction to transformers and generators to make the physics concrete.