magnetism - electromagnets Flashcards
what happens when current flows through conducting wire?
a magnetic field produced around the wire
how do we prove there is a magnetic field around wire when current flowing?
by using a compass. when current turned off, needle lines up with earths magnetic field. however if we turn current on again then the compass needle deflects. this proves magnetic fields round wire when
what does strength of magnetic field around a wire depend on?
larger current = stronger magnetic field
magnetic fields also strongest closer to the wire. as we move further, strength of magnetic field decreases
what happens to magnetic field if we change direction of current? what would happen to compass now?
we change direction of the magnetic field as we have reversed direction of convection current. compass placed near this wire will deflect in opposite direction to before
how do we work out the direction of magnetic field produced by a wire?
use the right hand grip rule. we place right hand so thumb pointing in direction of conventional current. now fingers are pointing in the direction of the magnetic field
another way to create a magnetic field in a wire carrying an electric current?
coil the wire in solenoid shape. when we turn on the current we get a strong and uniform magnetic field inside the solenoid. the magnetic field around a solenoid is similar shape to the magnetic field around a bar magnet
how to work out direction of magnetic field in a solenoid shape?
apply right hand grip rule.
how to increase strength of the magnetic field produced by a solenoid?
- increase size of current
- increase number of turns of coil
- place a piece of iron inside solenoid. an iron core. this is called an electromagnet
why are electromagnets useful?
we can change the strength if the magnetic field by changing the size of the current. can turn it on or off
