P15 Flashcards
Magnet rules
like poles repel and unlike poles attract
magnet field lines
the magnetic field lines of a bar magnet curve around from the north pole of the magnet to the south pole
distance from magnet
the greater the distance from the magnet, the weaker the strength of the magnetic field
induced magnetism
magnetism created in an unmagnetized magnetic material when the material us placed in the magnetic field
permanent magnets
steel is used instead of iron to make permanent magnets, because steel does not lose its magnetism easily, but iron does
field lines around a wire
magnetic field lines around a wire are circles centred on the wire in a plane perpendicular to the wire
solenoids
- long coil of insulated wire
- used in devices where strong magnetic field needs to be produced
- magnetic field increases strength when current increases
- reverses direction of currents reversed
inside the solenoid
magnetic field is much stronger than if the wire was straight
- field lines parallel to axis of solenoid in the same direction
- uniform
outside the solenoid
- magnetic field lines bend around from one end to the other of solenoid
- each field line is complete loop, because it passes through the inside of solenoid
electromagnets
solenoid that has an iron core, current passed along wire magnetises the iron bar
scrap yard crane
- vehicles lifted using powerful electromagnets attached to cranes
- steel sticks to magnet when current passes through the coil
circuit breaker
- switch in series with an electromagnet
- when currents too large switch opens by electromagnet and stays open until manual reset
electric bell
electromagnet attracts iron armature which opens at a switch
the relay
current through coil of electromagnet magnetises the iron core which pulls armature onto the, this closes switch
the motor effect
- force increased if current or strength of magnetic field or length of conductor is increased
- reversed if direction of current or magnetic field is reversed
