p6 magnetism

what is a magnetic field

a region where a magnetic pole would have a force acting on it

what direction do magnetic field lines go

they go from north to south

how do you show how strong a magnetic field is using lines

the closer the magnetic field lines are together the stronger the magnetic field is

how do you draw attraction and repulsion using magnetic field lines

what are the 3 main materials that are magnetic and how do they behave

iron and its alloys(like steel), nickel, cobalt and they are always strongly attracted no matter the magnetic field direction

what is an induced magnet

when a magnetic material is affected by the field of a permanent magnet, the material acts as if an extension of the permanent magnet, developing poles in a fashion were it is attracted to the magnet. coils can also be used to create induced electromagnetism

what is the difference between how soft iron and steel magnetize

soft iron quickly loses its magnetism while steel keeps its for longer allowing it to be used to make permanent magnets, and soft iron is used in stuff like transformers.

what kind of magnetic field is formed by charge going through a wire

the current goes in a anticlockwise loop to the direction of flow. use the right hand thumb rule to determine current

how does the magnetic strength vary relative to the wire

the closer to the wire you get the stronger the magnetic field so the lines need to be drawn closer

what is a solenoid

a solenoid is a coil of wire that mimics the magnetic field of a real magnet when current is flown through it. more current through the coil means the magnetic field would be stronger

how can you investigate the direction of magnetic field

by putting a magnet in the center of a piece of paper, putting a compass at the start of the magnet and move it forward towards where the needle is facing, plotting the position

what is a solenoid

a coil of wire used to induce magnetism into a soft iron core

what happens to a current carrying wire when it interacts with a magnetic field

it experiences a force

what is flemings left hand rule and what is it used for

for determining in which direction a force would act on a wire with current

how do loudspeakers work

by powering electromagnets with ac current, a cone is vibrated and the ac signal is converted to sound

how do you determine the magnetic field acting on an electron beam

in an electron beam, the direction of current is opposite to the direction of electrons, and the force is whichever way the electrons curve

what happens to a current carrying coil in an electric field

it starts to rotate since the direction of current is in opposite directions on either side of the coil

what is a split ring commutator

2 pieces of metal that are split in the middle to allow a dc motor to keep rotating in one direction

how does a dc motor work

a split ring commutator is attached to a coil that spins in between 2 magnets, switching direction of current every half turn in order to keep rotating in the same direction

what is electromagnetic induction

it is the creation of an emf and sometimes current in a conductor which is experiencing change in magnetic field or is moving relative to magnetic field

how can you increase the amount of electromagnetic induction

you can increase the strength of the magnetic field, increase the speed of magnetic field change, increase the amount of coils of wire

what forces are experienced when an emf is induced on a wire

when an emf is induced on a wire it causes current to flow and generate a field that opposes the movement of the magnet

how does an ac generator work

a coil spins in between 2magnets and induces an alternating current on the wire

how does a transformer work

it changes the voltage of an alternating current by inducing a magnetic field into an iron core which then induces current into a current with different amount of coils in order to translate voltage

what is the formula for amount of coils in a transformer based on the input and output voltages

primary voltage/secondary voltage = number of turns on primary coil/number of turns on secondary coil

how is power delivered to homes from power stations

first, it goes through a step up transformer in order to get a higher voltage, since current is lower and therefore power loss is lower. then it travels across pylons and goes through a step down transformer before going to homes

what is the formula for power loss in a wire

power loss(P) = current(I)² * resistance(R)

how efficient are transformers

transformers are usually close to 100% efficient but in theoretical scenarios it is assumed as 100% efficient

what is the formula for current and voltage across the 2 coils of a transformer

primary current(Ip) x primary voltage(Vp) = secondary current(Is) x secondary voltage(Vs)