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7. Magnetism and electromagnetism

Magnets and electromagnets

4 lessons
7.1 Magnets and magnetic fields Magnetic poles and forces, permanent and induced magnets, magnetic fields and field lines, plotting a field with compasses, and the Earth's magnetic field. AQA Edexcel OCR 7.2 Electromagnetism: wires and solenoids The magnetic field around a current-carrying wire, the right-hand grip rule, solenoids and electromagnets, and what affects the strength of an electromagnet. AQA Edexcel OCR 7.3 The motor effect and Fleming's left-hand rule Higher tier: the force on a current-carrying wire in a magnetic field (the motor effect), Fleming's left-hand rule, and the equation F = BIl with magnetic flux density in tesla. Higher only AQA Edexcel OCR 7.4 Electric motors How a simple d.c. motor works: a coil in a magnetic field, the forces on its two sides, the split-ring commutator and brushes, and how to make it turn faster. AQA Edexcel OCR

Electromagnetic induction

4 lessons
7.5 Loudspeakers and microphones Higher tier: how a loudspeaker uses the motor effect to turn an alternating current into sound, and how a moving-coil microphone uses electromagnetic induction to turn sound into an alternating potential difference. For Separate Science. Higher only Separate only AQA Edexcel OCR 7.6 Electromagnetic induction Higher tier: electromagnetic induction, how a changing magnetic field or a moving conductor induces a potential difference, the factors that affect its size and direction, and why the induced current opposes the change. Higher only AQA Edexcel OCR 7.7 Generators: alternators and dynamos Higher tier: how a generator works using a rotating coil in a magnetic field, alternators with slip rings giving a.c., dynamos with a split-ring commutator giving d.c., and the effect of rotating faster. For Separate Science. Higher only Separate only AQA Edexcel OCR 7.8 Transformers Higher tier: how a transformer changes the size of an alternating potential difference, step-up and step-down transformers, Vp/Vs = Np/Ns, Vp Ip = Vs Is for an efficient transformer, and why transformers need a.c. Higher only AQA Edexcel OCR