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