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Electricity

What is Power?

Power is an amount of energy supplied in a certain time.
Power is measured in watts.
Energy is measured in joules.

1 watt = 1 joule per second.

The word "per" means "divided by",
so power = energy ÷ time.     P = E ÷ t.

Since 1 volt = 1 joule per coulomb
and 1 amp = 1 coulomb per second

then watts = volts x amps,
or power = voltage x current

P = V x I

This equation is important!

The above equation can be rearranged to give
I = P ÷ V  and  V = P ÷ I

On the next page we shall see how to calculate the power
of any electrical component using a lamp as our example.

We can rearrange power = energy ÷ time
to give energy = power x time.    E = P x t.

Since power = voltage x current (see above)
if we write V x I instead of P
in the above equation we get E = V x I x t.
energy = voltage x current x time.

See all equations for electricity.

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