P15 - Magnets Flashcards
like poles
repel
unlike poles
attract
magnetic materials eg
iron or steel
permanent magnets are made from
steel
why are permanent magnets are made from steel instead of iron
-doesn’t lose its magnetism easily
-iron loses it easier
magnetic field
any other magnetic material placed in this space will experience a force caused by the first magnet
magnetic field line are more concentrated
at poles
magnetic field lines direction
always north to south
greater distance from magnet
weaker strength of magnetic field lines
induced magnetism
magnetised by placing in a magnetic field
induced magnetism poles of rod and magnet
nearest pole of rod and magnet always have opposite polarity
magnetic field lines in current carrying wire
magnetic field lines surround it
corkscrew rule
right hand
thumb = direction of current
fist = direction of field lines
corkscrew principle
reversing direction of current
reverses direction of magnetic field
solenoids
long coil of insulated wire
solenoid magnetic field lines produced
produced when current passes through
solenoids magnetic field lines increases strength when
current is increased
inside solenoid magnetic field lines
field is much stronger than if wire was straight
-field lines are stronger + uniform
-parallel to axis of solenoid + same direction
outside solenoid magnetic field lines
-similar to lines of a bar magnet
-complete loop as it passes through inside
the current flows which direction from the view of the s pole
clockwise
the current flows which direction from the view of the n pole
anti clockwise
solenoid rule
-wrap finger in direction of current
- thumb of right hand points to north pole
electromagnets switched off
current switched off = loses its magnetism
electromagnets
solenoid is wrapped around iron core
-current passes through wire = mg field
-magnetises iron core
mg field lines around current carrying conductor
circles centred onto wire
-in a perpendicular plane to wire
scrapyard crane
lifts steel frame of cars
drops when circuit is cut
circuit breaker
current is too large
-switch is opened by EM
EM uses eg
scrapyard crane
circuit breaker
electric bell
relay
circuit breaker, relay, electric bell works by
-attracting an iron armature which opens a switch
