5.91. Electric Transformers http://www.ck12.org
5.91 Electric Transformers
- Describe an electric transformer and how it changes electric current.
- Distinguish between step-up and step-down electric transformers.
You’ve probably noticed big drums like this one at the tops of electric poles. A pole close to your home is likely
to have one. The drum is an electric transformer. Without it, the current entering your home would have too much
voltage for your home’s electric circuits to handle.
What Is an Electric Transformer?
Anelectric transformeris a device that uses electromagnetic induction to change the voltage of electric current.
Electromagnetic induction is the process of generating current with a magnetic field. It occurs when a magnetic field
and electric conductor, such as a coil of wire, move relative to one another. A transformer may either increase or
decrease voltage. You can see the basic components of an electric transformer in theFigure5.194. For an animation
showing how a transformer works, go to this URL: http://www.youtube.com/watch?v=VucsoEhB0NA.
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/82411The transformer in the diagram consists of two wire coils wrapped around an iron core. Each coil is part of a
different circuit. When alternating current passes through coil P, it magnetizes the iron core. Because the current is
alternating, the magnetic field of the iron core keeps reversing. This is where electromagnetic induction comes in.
The changing magnetic field induces alternating current in coil S of the other circuit.