Electric Circuits

Charge and current, potential difference and resistance, Ohm's law, resistivity, series and parallel circuits, and EMF with internal resistance.

Electric circuits move charge around a loop, transferring energy from a source to components.

Current, potential difference and resistance

Current

I = \dfrac{Q}{t}

(A) — rate of flow of charge.

Potential difference

V = \dfrac{W}{Q}

(V) — energy per unit charge transferred.

Resistance

R = \dfrac{V}{I}

(Ω).

Ohm's law: for an ohmic conductor at constant temperature, $V \propto I$ (a straight-line $I$ – $V$ graph through the origin).

A simple series circuit: the same current flows through R₁, R₂ and the ammeter.

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