Electric current

Electric current is the rate at which electric charge passes through a surface. Its SI unit is the ampere, equal to one coulomb per second.

Electric charge: A conserved physical property that causes particles and objects to exert electromagnetic forces. Current measures how quickly this property crosses a chosen surface.
Ampere: The SI unit of electric current, defined by fixing the elementary charge at an exact value. It gives the standard unit for the rate of charge flow.
Electric circuit: An arrangement of components and conducting paths through which electric charge can flow. Circuit analysis tracks how current flows through connected components.
Direct current: Electric current whose direction remains constant over time. It is the steady-direction case, even if its magnitude varies.
Current density: A vector field describing electric current per unit area and its direction at each point. It resolves total current into its local distribution across a surface.
Elementary charge: The magnitude of the charge carried by a proton or electron, approximately 1.602 × 10⁻¹⁹ coulombs. Individual carrier charges add up to the charge transported by a current.
Ammeter: An instrument designed to measure electric current in a circuit. It measures current by being connected in series with the path.
Alternating current: Electric current that periodically reverses direction, usually with a repeating waveform. It contrasts with current whose direction stays fixed.
Conventional current: The defined direction of electric current, from positive toward negative potential in a circuit. Its direction remains fixed by convention even when electrons drift oppositely.
Electric potential difference: The change in electric potential energy per unit charge between two points, measured in volts. Potential difference often drives charge transport through a circuit.

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