Electricity

Watts

Power is measured in Watts.
Power is an amount of energy supplied in a certain time.

1 Watt = 1 Joule per second.

The word "per" means "divided by",
so Power = energy ÷ time.     P = E ÷ t (see equations).

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 very important!

On the next page we shall see how to calculate the power of a lamp.

Since from the above, power = energy ÷ time,

then   energy = voltage x current x time,
E = V x I x t.