Current, potential difference and resistance

Standard circuit diagram symbols

Electrical charge and current

For electrical charge to flow through a closed circuit the circuit must include a source of potential difference.

Current is the flow of electrical charge around a circuit.

The charge in an electrical circuit is carried by electrons.

Current is measured in amps using an ammeter.

Current only flows in one direction in a series circuit and is produced by a source of potential difference.

Charge flow=current*time

charge flow, Q, in coulombs,

C current, I, in amperes, A (amp is acceptable for ampere)

time, t, in seconds, s

A current has the same value at any point in a series circuit.

Current, resistance and potential difference

The current through a component depends on both the resistance of the component and the potential difference across the component.

The greater the resistance of the component the smaller the current for a given potential difference (pd) across the component.

Potential difference is the energy transferred for each coulomb of charge between two points in a circuit.

The voltmeter is attached in a parallel circuit.

potential difference = current × resistance

potential difference, V, in volts,

current, I, in amperes, A (amp is acceptable for ampere)

resistance, R, in ohms, Ω

Resistors