Transformer презентация

Transformers
primary coil
secondary coil
A transformer changes the peak value of an alternating voltage.
Transformers consist of two coils: the primary coil and a secondary coil.
When an alternating voltage passes through the primary coil, an alternating magnetic field is created, which induces an alternating e.m.f. in the secondary coil.

The transformer rule
Ns
NsΦ
Np
NpΦ
Dividing the equation for the e.m.f. of the secondary coil by the one for the primary coil gives the transformer rule:
In a step-up transformer: Ns > Np so Vs > Vp.
In a step-down transformer: Ns < Np so Vs < Vp.

Transformer efficiency
The efficiency is very high for a typical transformer. A laminated core reduces eddy currents, the wires have very low resistance and a soft iron core allows easy magnetizing/demagnetizing.
In a step-up transformer, voltage is stepped up and current is stepped down.
In a step-down transformer, voltage is stepped down and current is stepped up.

Glossary

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Magnetic fields: equations summary