p2 topic 7 - magnetism and electromagnetism

what is an induced magnet

magnets that are ‘magnetic’ but do not have fixed poles

how can induced magnets be made into temporary magnets

stroking them with a permanent magnet

why is stroking an induced magnet effective

aligns the domain in the material all in the same direction

what are examples of induced magnets

iron, nickel, cobalt

what does a current produce

a magnetic field around the wire

how is the direction of current decided

right hand grip rule

what happens when there is a greater current

stronger magnetic field

what happens when there is a greater distance from the wire

weaker field

what is a solenoid

a coil of wire that becomes an electromagnet when an electric current flows through it

how does a solenoid enhance a magnetic effect

the coiling of the wire causes the field to align and form a giant single field

how does an iron core increase the strength of a magnet

easier for magnetic field lines to pass through than air

what are factors that affect the strength of a magnet

coils, current, core

what are ferromagnetic materials

magnetic materials that become magnetised when placed in the field of the permanent magnet. they are always attracted to the magnet

why are electromagnets different

youcan turn an electromagnet on and off by turning the current on and off

what does the thumb present in fleming’s left hand rule

force (f)

what does the second finger present in fleming’s left hand rule

magnet field (b)

what does the middle finger present in fleming’s left hand rule

current (i)

when is the force strongest

when the current is perpendicular to the magnetic field

how can the size of the force be calculated

f=bil

what is electromagnetic induction

the production of a potential difference when a conductor is in a changing magnetic field

how the direction of the induced current be reversed

the wire is moved in the opposite direction, the field is reversed

how can the size of the induced current be increased

increasing the speed of the movement, increasing magnet strength

what is lenz’s law

the induced potential difference produced in a direction such that the magnetic field produced opposes the change that created it