Revision Notes

Charge / Current / Voltage / Resistance


  • The charge is the amount of electricity travelling through a circuit
  • The symbol for charge is Q
  • The unit for charge is coulombs
  • A capacitor is a device that stores charge
  • Charge (Q) = current (I) x time (t)

This is the flow of electrons round the circuit. This is measured in amps (I)

This is the driving force that pushes the current round. This is measured in volts (V)

This is anything in the circuit that slows the flow of current down. This is measured in ohms (W)

Ohm’s Law shows that:

  • Voltage (V) = Current (I) x Resistance (R)

So if you increase the resistance then less current will flow if the voltage remains constant.

If you increase the voltage then more current will flow, if the resistance is constant.