Topic explanation

Standard explanation

Electric current is the rate of flow of charge through a cross-section.

Key points

• Electric current is the rate of flow of charge through a cross-section.
• Average current is Iavg=ΔQΔt; instantaneous current is I=dQ/dt.
• For constant current, transferred charge is Q=It.
• The SI unit is the ampere: 1 A=1 C·s⁻¹.
• Conventional current follows the direction of positive-charge flow.
• In a metal, electron drift is opposite to conventional current.
• An ammeter is connected in series and has very low resistance.
• If N electrons pass, Q=Ne and N=It/e.

Labelled diagram