Magnetism Flashcards
What are four properties of magnets
Magnets attract magnetic materials
Magnets have two poles
A freely suspended magnet comes to rest in the north-south direction
Like poles repel, unlike poles attract
Define magnetic induction
A process whereby an object made of a magnetic material becomes a magnet when placed close to a strong magnet or within a current-carrying solenoid
Why do paper clips attracted to a magnet fan apart
A paper clip attracted to magnet becomes induced magnet that attracts other clips. The clips at the lower end fan apart as like poles are induced at the lower ends and they repel each other
Describe magnetising magnetic materials by stroking
Unmagnetised steel bar is stroked several times from one end to another, pin one direction, with one pole of a permanent magnet. Stroking magnet should be lifted sufficiently high above steel bar between successive strokes. Pole produced at end of steel bar where strokes finish is opposite to stroking pole used.
Describe magnetising using dc
Large direct current flows through coils of wire, a solenoid, a strong magnetic field is produced. Magnetic field aligns tiny magnets in steel bar. After period of time, steel bar is magnetised
How to determine poles of a solenoid
Right hand grip rule, Curl fingers in direction of current flow and thumb points in direction of N-pole
Describe demagnetising of magnet by heating
Strongly heating a magnet and letting it cool in east-west direction will cause magnet to lose magnetism. Atoms of magnet vibrate vigorously when heated, causing ‘tiny magnets’ within magnet to lose their alignments
Describe demagnetising of magnet by hammering
Hammer a magnet placed in east-west direction to alter alignment of ‘tiny magnets’ within magnet, causing magnet to lose magnetism
Define magnetic field
Magnetic field is a region in which force of magnetism acts
Define temporary magnet
Magnets that retain magnetism in presence of electric current or permanent magnetic field
Define permanent magnet
They do not require the presence of an electric current or permanent magnetic field to retain their magnetism
What kind of magnetic material (hard/soft) is used in a loudspeaker
Hard magnetic material e.g. steel
