Electricity is the flow of electrically Charged particles. The particles can gain and lose energy as

they move around the circuit.

Definitions:

• The current is the number of coulombs of charge passing a point every second. One coulomb of charge is 6 x 10^{18} charged particles. The units for current are coulombs per second, CS^{-1} or amps (A).

• Voltage is amount of energy that each coulomb of charge carries. The units for voltage are joules per coulomb, JC^{-1} or volts (V).

• Resistance is the measure of the opposition to the flow of electrical current. The units for resistance are volts per coulomb, VC^{-1} or ohms (Ω).

• Power is the rate of doing work. It is measured in the number of joules of energy transferred every second, JS^{-1} or watts (W).

For simplicity when drawing electrical circuits, symbols are used. These symbols: