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Generators and transformers (Generators (a generator consist of a coil of…
Generators and transformers
Generators
a generator consist of a coil of wire that is rotted inside a magnetic field
As the coil turns, a voltage is induced in the wire.
the ends of the coil are connected to
slip rings
electrical contact with an external circuit is made using
carbon brushes
, which press on the slip rings.
A generator like this produces
alternating current
, and is often called an
alternator
Generators used in power stations and the alternators in cars work on similar principles but have a rotating electromagnet surrounded by coils of wire.
Transformers
If the voltage (potential difference) of the electricity passing through the wires is increased, the current is decreased
when the current is smaller, less energy is transferred to heating and so the efficiency is improved.
Power stations produce electricity at 25kV
This is changed to 400 kV by
transformers
before the electricity is sent around the country.
the voltage is reduced before the electricity is sent to factories and other buildings.
Different transformers
A step-up transformer
increases the voltage and decreases the current at the same time
A step-down transformer
makes the voltage lower and the current higher
How do transformers work?
a transformer is made using 2 coils of insulated wire wound onto an iron core.
there is no electrical connection between the 2 coils of wire
Transformers only work with alternating current, when the direction of the potential difference changes many times each second.
The alternating current in the primary coil creates a continuously changing magnetic field, and the iron core of the transformer carries this magnetic field to the secondary coil.
The changing magnetic field induces a changing potential difference in the secondary coil .
The P.D is greater in the secondary coil because it has more turns than the primary coil.
the potential difference across the coils of a transformer can be worked out using this equation:
