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Overview
Electric current describes the flow of electric charge. In circuits, current is the rate at which charge passes a point. Current is essential for operating electrical devices because moving charge can transfer energy to bulbs, motors, heaters, electronics, and other components.
Charge Flow
Current is charge flow per unit time. A larger current means more charge passes a point each second.
Conventional Current
Conventional current is defined as the direction positive charge would flow. In metal wires, electrons usually drift in the opposite direction, but conventional current remains the standard circuit direction.
Electron Drift
Electrons in a metal move randomly at high speeds, but an electric field causes a slow net drift. This drift produces current.
Complete Circuit
A continuous conducting path is required for steady current. If the circuit is open, charge cannot continue circulating through the loop.
Direct and Alternating Current
Direct current flows in one overall direction. Alternating current reverses direction periodically and is used in many power systems.
Measuring Current
An ammeter measures current and is connected in series so the circuit's charge flow passes through the meter.
Current and Energy Transfer
Current carries charge through devices, but voltage determines energy per charge. The combination of voltage and current determines electrical power.
Common Mistakes
A common mistake is thinking current is used up by circuit components. Current flows through a series circuit, while energy is transferred by charges as they move through components.
Why This Matters in Physics
Current is foundational for circuits, resistance, Ohm's law, electrical power, electronics, magnetism, motors, and generators.