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Current, Charge & Power – joules, coulombs, amps, volts, watts.


Electrical current is the rate of flow of charge in a circuit. Current (I) is measured in amps (A), using an ammeter.


Charge (Q) is measured in coulombs (C). Each electron carries a tiny amount of charge, 1.6 x 10-19 coulombs.

charge               =      current           x         time

(coulomb, C)        (ampere, A)             (second, s)


Power (P) is the rate at which energy is transformed in a device, it is measure in watts (W). 1 watt means that 1 joule of energy is transformed in one second.

power                   =           energy transformed


Power, potential difference and current are related by the following equation;

power                =             potential difference     x       current

The energy transformed is given by;

energy transformed          =         potential difference      x      charge