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Electricity

Mains Electricity - Alternating Current.

What is Alternating Current?

Alternating current is different from direct current.

With alternating current (symbol a.c.)
the electrons first start to flow in one direction
until the current reaches a maximum value.
The current is here given a plus sign to show
that it is in the forward direction.
The current then slows down and stops.

The electrons then start to flow in the reverse
direction until the current reaches the same
maximum value. The current is here given a minus
sign to show that it is in the reverse direction.
The current again slows down and stops.

The whole cycle of going from a maximum value
to zero, and plus to minus
then repeats itself over and over again.

The number of cycles in one second is called
the frequency.  The frequency is given in a unit
called hertz (symbol Hz)
where 1 Hz = 1 cycle per second.

Mains electricity in the UK is
supplied at 50 Hz (50 cycles per second).
In the USA it is 60 Hz.

Continued on the next page.

All of the equations for direct current circuits
also apply to alternating current circuits.
Voltage, current, power, energy, resistance etc
can all be calculated in the same way.

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