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Brainlag Learn / GCSE Physics

Magnetism and electromagnetism

Magnets and field lines, electromagnets, the motor effect and F = BIl, then loudspeakers, induced potential difference, generators, microphones and transformers.

Lessons

  1. Magnets and magnetic fieldsPoles that attract and repel, permanent and induced magnets, field lines, and how a plotting compass shows the Earth's field. 20 min, free
  2. ElectromagnetismThe field around a wire and a solenoid, the right-hand grip rule, what makes an electromagnet stronger, and where electromagnets are used. 20 min, free
  3. The motor effectThe force on a current in a magnetic field, Fleming's left-hand rule, F = BIl with the tesla, and why the coil of a motor keeps turning. 25 min, Plus
  4. Loudspeakers and induced potential differenceHow a loudspeaker uses the motor effect, then the reverse: moving a magnet and a coil induces a potential difference, what makes it bigger, and which way the current flows. 25 min, Plus, Physics only
  5. Alternators, dynamos and microphonesTurning a coil in a field gives a.c. through slip rings or d.c. through a commutator; reading peak, period and frequency off the output graph; and how a moving-coil microphone works. 20 min, Plus, Physics only, Higher tier
  6. TransformersTwo coils on an iron core: how a transformer works, step-up and step-down, the turns ratio Vp/Vs = np/ns and power in = power out for an ideal transformer. 25 min, with the Scientific Calculator, Plus, Physics only, Higher tier

Practise and test

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