IGCSE MAGNETISM AND ELECTROMAGNETISM
DEFINITIONS AND CONCEPTS
HARD AND SOFT MAGNETIC MATERIALS: Materials, which are difficult to magnetise and de-magnetise. Soft materials are easy to magnetise and de-magnetise.
MAGNETIC FIELD: The area around a magnet where another magnet would feel a force.
MAGNETIC FIELD LINES: Show the direction of the magnetic field. The lines run from North to South. Where the field is strong, they are close together.
INDUCED MAGNETISM: A magnetic material can be magnetised by being placed in a magnetic field.
ELECTROMAGNET: A current-carrying coil of wire (SOLENOID) often wrapped around a soft magnetic core which produces a magnetic field quite like a bar magnet with uniform field lines inside.
MOTOR EFFECT: A current-carrying wire in a magnetic field experiences a force. This effect is applied in simple DC motors, loudspeakers and ammeters. The force is greater when the field or current are greater.
LEFT HAND (MOTOR) RULE: With the First finger, second finger and Thumb at right angles to each other, we can model respectively Field, Current and Thrust (Motion) on a conductor.
ELECTROMAGNETIC INDUCTION: A changing magnetic field through a conductor will induce a voltage in the conductor. The voltage is greater when the change is greater (larger field or faster movement).
GENERATOR/ DYNAMO: A device, which induces a voltage when a magnet rotates in a coil or vice versa. A larger voltage is induced when the rotation is faster, the field greater or there are more turns in the coil.
TRANSFORMER: A device, which allows an input AC voltage to be stepped up or down.
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