electricity and magnetism- topic 4 Flashcards
what happens when magnets are free to move
they line up with the earths poles
what are magnetic materials
iron and steel, nickel and cobalt
(materials that can be used to make magnets, can be magnetised easily)
what does it mean to be magnetically soft/ hard
soft= loses its magnetisim easily
hard= retains its magnetism
what are permenant magnets made of
steel, because its magnetically hard
attraction and repulsion law
oposites attract, like poles repulse
explain induced magnetism
stroke a steel nail with a permanent magnet
steel becomes a magnet
how may a magnet be demagnetised
heating and/ or hitting with a hammer
more effective if placing magnet inside ac coil and slowly removing it
magnetic field
region where a magnetic pole experiences a force
always from north to south
how are iron fillings used
to show the magnetic field lines around a magnet (from n to s)
what is the only test for magnets
repulsion
how do you make a permenant magnet
place steel rod inside coil use high dc current for some time, turn current off and then remove rod
how do you increase the strength of an electro magnet
use iron core
more current
more turns in wire
what are examples of electromagnet
electric bells
loud speakers
some microphones
scrap car lift
properties of permenant magnets vs temporary
permenant- permenantly mgnetised, made of steel, magnetism doesnt vary in strength, magnetic poles cant be altered
temporary magnets- temporarily magnetise, made of soft materials, magnetism can be varied in strength, magnet poles can be altered
state difference between magnetic or non magnetic materials
magnetic materials can also repulse along with attracting, non magnetic can only attract not repulse
what is the direction of a magnetic field at a point
the direction of a magnetic field at a
point is the direction of the force on the N pole of a magnet at that point
what are magnets
objects which experience attraction and repulsion
like poles repulse
unlike poles attract
describe magnetic materials
Experience a force when placed in a magnetic field
Are attracted to a magnet when unmagnetised
Can be magnetised to form a magnet
are not repulsed
describe non magnetic materials
Non-magnetic materials do not experience a force when placed in a magnetic field
describe uses for permenant magnets
compasses- navigation
toys, fridge magnets
describe electromagnets
Electromagnets use electricity to create a magnet from a current-carrying wire
They have the advantage that they can be magnetised and demagnetised, literally at the flick of a switch
They can be switched on and off
Soft iron is the metal normally used for this
It can easily become a temporary magnet
describe uses for electromagnets
mri scanners, speakers/ headphones,
how is the relative strength of a magnetic field represented in a drawing
by the proximity of the lines
closer= stronger
what are magnetic forces due to
interactions between magnetic fields