Transformers

• AC currents can be increased or decreased by using a transformer.

• Consists of a primary coil, a secondary coil and an iron core.

• The iron core gets magnetized by the incoming current and this magnetism then creates a current in the leaving wire.

• The power is the same on both sides (assume= 100% efficiency).

• You can figure out number of coils and the voltage with:

(Under 100% efficiency)

• When magnetic field is changed across the primary coil by connecting it with A.C. an e.m.f. induces across the secondary coil.

• The iron core channels the alternating field through the secondary coil, inducing an alternating e.m.f. across it.

• A step-up transformer increases the voltage and a step-down transformer decreases it.

• Transformers used to make high voltage AC currents.

• Since power lost in a resistor , having a lower current will decrease the power loss.

• Since transmission cables are many kilometres long they have a lot of resistance, so a transformer is used to increase the voltage and decrease the current to decease power lost.

• The advantages of high-voltage transmission:

  • Less power lost

  • Thinner, light, and cheaper cables can be used since current is reduced