Electromagnetic Induction Flashcards
what is electromagnetic induction?
the induction of a potential difference in a wire which is experiencing a change in magnetisms field
how do you affect the direction of the potential difference?
if you move or rotate the magnet in the opposite direction, the pd or current will be reversed
how do you produce an alternating current?
if you keep the magnet moving backwards and forwards, or keep it rotating in the same direction, you produce an alternating current
how do you increase the size of the induced pd?
by increasing the strength of the magnetic field
increasing the speed of movement
having more turns per unit length on the coil of wire
describe how the magnetic field produced opposes the original change
when a current is induced in a wire, that current produces its own magnetic field
the magnetic field made by an induced current always acts against the change that made it
how do alternating currents in one circuit induce another current in another circuit in a transformer?
when an alternating pd is applied across the primary coil it produces an alternating magnetic field
the iron in the core - is magnetised and demagnetised
this changing magnetic field induces a pd in the secondary coil
why is the iron in the core of a transformer easily demagnetised and magnetised?
Because the coil is producing an alternating magnetic field, the magnetism in the core also alternates
what else can transformers do?
they can change the size of an alternating voltage
input power and output power equation
v(primary) x I(primary) = V(secondary) x I(secondary)
where are step up transformers used?
at power stations to boost the pd up really high and keep the current relatively low
where are step down transformers used?
at houses, they bring the voltage back down to keep it safe and unsafe levels at consumers end
why do transformers produce a high voltage and low current?
high current makes wires heat up so lots of energy is wasted to thermal stores
so to reduce heat loss and make the national grid more efficient, high voltage, low resistance cables and transformers are used
