Simple Phenomena of Magnetism
magnets
have magnetic field around them
2 opposite poles(north and south)
like poles repel, unlike poles attract
attract magnetic materials by inducing(permanent or temporary) magnetism in them
exert little/no force on non-magnetic material
induced magnetism
magnet attracts materials by inducing magnetism in them
material becomes magnet
side of material facing magnet will become opposite pole as magnet
ferrous(magnetic materials)
iron, nickel, cobalt
non-ferrous(non-magnetic materials)
plastic, wood, rubber
methods of inducing magnetism
place steel near magnet(magnetism is weak)
stroking it with one end of magnet in one direction
place in solenoid and pass large direct current through coil
methods of demagnetisation
smash with hammer, drop it
heat to high temperature
solenoid method but with alternating current
iron vs steel
soft iron
get margnetized fast but easily lose magnetism
high susceptibility, low retentivity
use: core in transformer
steel
get magnetized slow but acquire magnetism long
low susceptibility, high retentivity
use: making magnets
permanent magnet vs electromagnet
permanent magnet
hard magnetic material
use: fridge doors, etc
electromagnet
use solenoid to create magnetic field
use: scrap metal moving, etc