Electricity is the flow of electrically Charged particles. The particles can gain and lose energy as
they move around the circuit.
• The current is the number of coulombs of charge passing a point every second. One coulomb of charge is 6 x 1018 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: