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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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