Magnetic Fields Flashcards
what is the relation between like and unlike magnetic poles?
- N and N repulsion
- S and N attract- uniform field
when drawing magnet poles which was do the arrows go?
north to south
-closer lines together stronger the magnetic field
what is a permanent magnet?
- i.e bar magnets
- produce own magnetic field all the time
what is a induced (temporary) magnet?
only produce magnetic field while they’re in another magnetic field
what are the 3 main magnetic elements?
iron, nickel, cobalt
what alloy of the main magnetic elements are magnetic?
steel- alloy of iron
how does a compass relate to evidence that the core of the earth must be magnetic?
- always points to north pole
- because earth generates own magnetic field
what are permanent magnets?
- eg bar magnets
- produce their own magnetic fields all the time
what are induced magnets?
-only produce magnetic field when in another magnetic field
what does a moving charge through a long straight conductor (wire) create?
magnetic field
how do you work out how large the current is around a wire?
- closer to wire stronger the current
- closer circles are stronger the current
what does the right hand thumb rule show you?
the direction of the magnetic field
how do you do the right hand tub rule?
thumb points in the way of the current so the fingers follow in the way of the magnetic field
what does the strength of the field depend on?
- size of current
- distance form conductor
what is solenoid?
long coil of wire
what is a solenoid an example of?
an electromagnet
what do the individual fields in a solenoid do?
- add to form a strong uniform field along centre
- cancel to give weak field outside the solenoid
what happens when a current carrying a conductor is placed near a magnet?
magnet experiences a force and an equal opposite force acts on the magnet
what are magnetic forces due to ?
magnetic forces are due to interactions between magnetic fields
what is Flemmings left hand rule used to show?
represent directions of force, current, and magnetic field
how does Flemmings left Hand rule work?
- put first and second finger in an L shape and thumb up
- tumb= motion, force
- first finger= magnetic field
- second finger= current
- fit to a diagram and direct will be given
what is the equation to work out the size of a force?
F= B x I x L force(N)= magnetic density/flux (T) X current(A) X length (m)
what are the factors with effects the size and direction of created potential difference?
- increase strength of magnetic field
- more coils
- increase speed
how does the magnetic field produced oppose the original change?
- current produces own magnetic field
- magnetic field toys to act against the charge
what does induce mean?
create
what can a transformer do?
change the size of a alternating voltage
what is the national grid?
network of wires and transformers that connect Uk power stations to consumers (anyone who uses electricity)
why is energy transferred at different voltages at the national grid?
- high voltage from power stations
- lower voltage for domestic use
- improves efficiency by reducing heat loss in transmission lines
why are step up transformers used in the national grid?
boost p.d. high(400,000V) and keep current low
why are step down transformers used in the nation grid?
-bring down to safe and usable levels for consumer
what is the equation for transformers which are 100% efficient?
Vp X Ip = Vs X Is V= voltage (V) I= current (A) p= primary coil s= secondary coil
