Basics: Electricity

Electrical Charges

Electrical charges are measured in coulombs.

The flow of charges or current is measured in amperes (I).

(1 ampere = 1 coulomb per second)

Where 1 coulomb is the amount of electrical charge in 6.241506×1018 electrons or other elementary charged particles.

Electrical Power

Electrical power is the rate at which electrical charges are moved.

Electrical power is measured in watts (P).

(1 watt = 1 joule per second)

Where 1 Joule is the work required to move an electric charge of one coulomb through an electrical potential difference of one volt; or one coulomb volt, with the symbol C·V.

Electrical Energy

Electrical energy is the amount of electrical charge.

Electrical energy is measured in joules or watt-hours.


Voltage is the difference in charge across a conductor when a current of one ampere dissipates one watt of power.

 (1 volt = 1 joule per coulomb)

 Voltage determines how much current travels through a circuit with a given electrical resistance.

(1 volt = 1 ampere x 1 ohm)

Ohm’s Law

Resistance is a term that describes the forces that oppose the flow of current in a conductor.

1 ohm is the amount of electrical resistance that exists in an electrical circuit when 1 amp of current is flowing with 1 volt being applied to the circuit).

Voltage/Resistance=Current, V/R=I and V=IR

Joule’s Law

P=VI is the power dissipated in a resistor.  Combining with Ohm’s Law for V=IR: P=I2R , the I2  term explains why higher voltage systems can have more power with less power losses over the same diameter wire.