Physics Unit 3

The creation of a voltage in a wire which is experiencing a change in magnetic field

by moving a magnet in a coil of wire or moving conductor in a magnetic field

magnetic in opposite direction, voltage/current reversed

magnet/coilmoving backward and fowards, produces voltage that keeps swapping directions

Transformers change AC voltages

step up and step down transformers, both have two coils, the primary and the secondary

step up - steps the voltage up, more turns on the secondary coil

step down - steps the voltage down, more turns on the primary coil

primary coil -> magnetic field 

alternating current in primary coil -> field constantly changing direction

rapidly changing magnetic field felt by the secondary coil

primary voltage     = number of turns on primary

secondary voltage = number of turns on secondary

used on the national grid:

to transmit a lot of power, need high voltage or current

high current -> loss of power (as heat) -> resistance of the cables

cheaper -> voltage up to 400,000 V -> current very low

transformers step up the voltage at one end for efficient transmission, and steps it down at the other end, to safe usable levels