Definition
A magnet attracts magnetic materials (iron, nickel, cobalt) and has two poles, north and south, which can never be separated.
Like poles repel; unlike poles attract.
Remember
A magnet always attracts an unmagnetized magnetic material (either pole works), but attracts or repels another magnet depending on which poles face each other — this is the standard way to test whether an unknown magnetized bar is really a magnet.
Definition
The magnetic field is the region around a magnet where its magnetic effect can be felt. Field lines run from the north pole to the south pole outside the magnet, never cross, and are closer together where the field is stronger.
Definition
A magnet can be made by stroking a magnetic material with an existing magnet, or by placing it inside a current-carrying solenoid (electromagnet).
Demagnetization (losing magnetism) happens by heating, hammering, or dropping a magnet repeatedly.
Remember
An electromagnet's key advantage over a permanent magnet: its strength and polarity can be controlled (and switched off) using the current — used in electric bells, cranes for lifting scrap metal, and loudspeakers.
Magnetic recording (tapes, hard disks) stores information by magnetizing tiny regions of a material in patterns; permanent magnets are usually made of hardened steel or special alloys that resist demagnetization.
Quick Recap
- ●Magnets have two inseparable poles; like poles repel, unlike attract
- ●A magnet always attracts an unmagnetized magnetic material, whichever pole is used
- ●Field lines: north to south outside the magnet, never cross, closer together = stronger field
- ●Magnets are made by stroking or by a current-carrying solenoid; lost by heating, hammering or dropping
- ●An electromagnet's strength/polarity is controllable via its current, unlike a permanent magnet
