Ch 13 covers the magnetic effects of electric current — Oersted's discovery, magnetic field patterns, right-hand rules, electromagnets, electric motor, electromagnetic induction, and electric generator.
Oersted discovered that electric current produces a magnetic field. Field lines around a straight conductor: concentric circles (right-hand thumb rule: thumb = current direction, curled fingers = field direction). Solenoid: tightly wound coil, field inside is uniform and resembles a bar magnet. Electromagnet: solenoid with soft iron core — strong, controllable magnet.
Current-carrying conductor in a magnetic field experiences a force (F = BIL). Direction: Fleming's left-hand rule (First finger = Field, seCond = Current, thuMb = Motion). Electric motor: converts electrical energy to mechanical energy using this force — coil rotates between magnets. Split ring commutator reverses current every half turn.
Changing magnetic field induces EMF/current in a coil (Faraday). Direction of induced current: Fleming's right-hand rule. Electric generator: converts mechanical to electrical energy. AC generator: slip rings → alternating current. DC generator: split rings → direct current. Domestic supply: AC at 220V, 50 Hz.
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An electric motor converts electrical energy into mechanical energy (rotation) — it uses current in a magnetic field to produce force. A generator does the opposite — it converts mechanical energy into electrical energy by rotating a coil in a magnetic field, inducing current. The principle is the same; the energy conversion direction is reversed.
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