Electric Current
Electric current is the rate of flow of electric charge. I = Q/t. SI unit is the ampere (A).
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Definition of electric current
Electric current is the rate at which electric charge flows through a cross-section of a conductor. Mathematically, I = Q/t, where Q is the charge passing through in time t. The SI unit of current is the ampere (A): 1 A = 1 C/s. Current is a scalar; direction is indicated by the sense of flow (conventional current is from positive to negative).
Conventional current vs electron flow
Conventional current is defined as the direction in which positive charges would move—from the positive terminal of a battery toward the negative. In metals, charge is carried by electrons, which move in the opposite direction. For most circuit analysis we use conventional current.
Direct and alternating current
Direct current (DC) flows in one direction only (e.g. from a battery). Alternating current (AC) reverses direction periodically (e.g. mains supply). Ohm's law and basic circuit rules apply to DC and to instantaneous values in AC.
Why do we use conventional current (positive to negative) when electrons actually move the other way?