Electric Transformers
Created | Updated Jan 28, 2002
This should at somepoint become a entry about electric transformers.
Source 1
A transformer consists of two coils of wire wrapped around a iron core. When an a.c. current is applied to one coil, a continually changing magnetic field is formed around the core. This causes an alternating voltage to be induced in the other coil. The diagram below shows a transformer.
| Picture: Transformer and lamp |
The a.c. voltage applied to the primary coil or winding induces an alternating voltage in the secondary coil. energy is transfered through the changing magnetic field.
Tranformers come in two varieties: step-up transformers and step-down transformers. A step-up transformer increases the voltage by having more second windings, while a step-down transformer decreases the voltage by having fewer secondary windings.
The ratio of the voltages on the two coils is equal to the ratio of the windings on the two coils:
| Vp Np -- = -- Vs Ns |
The ratio of the currents in the coils of a transformer is the inverse ratio of the turns or voltages:
| Ip Ns -- = -- Is Np |
Transformers are very efficient and it is assumed that all the power is transfered between the coils:
| Vp×Ip = Vs×Is |
