Transformers

Transformers

1. Electromagnetic induction

   • Electromagnetic induction is the process of creating a current by passing a conduct through an electromagnetic field.
     • This happens because the magnetic field causes electrons to move, the negative electrons go to one end and the positive electrons go to the other, this creates a potential difference which creates a flowing current in the conductor.
       • Generaters produce a current by rotating a coil within a magnetic field.

2. Transformers in the national grid

   • The national grid is a network of cables, transformers and generators which are designed to generate and transport electricity effectively.
     • In the transporting cables, very high voltages are used to reduce power loss in the cables, this would be caused by the heating effect of a current. The higher the voltage, the lower the current, this means energy loss through heat is reduced.
       • A transformer is made up of two coils, a primary coil and a secondary coil. If the number of coils in the primary coil is more then in the secondary coil the voltage in the primary coil will be greater, this means it is a step down transformer (it decreases voltage). If the number of turns in the secondary coil is greater then the number of turns in the primary coil, voltage in the secondary coil will be greater, therefore it is a step up transformer (it increases voltage)
         • Voltage in primary coil / voltage in secondary coil = No. of turns in primary coil / No. of turns in secondary coil
         • Steps down transformers are used to turn the voltage to a safe and usable level.
           • Transformers can only work with alternating currents, because the need a changing magnetic field in order to induce a current in the second coil.
             • Rectifiers can change ac supplies into dc supplies