Electric current — common mistakes

Always remember that conventional current is defined as the direction positive charges would flow, even though in most metallic conductors, it's the negatively charged electrons that are actually moving in the opposite direction. Be careful with this distinction in exam questions!

Charge is a fundamental property of matter, like mass, existing as positive or negative. It's measured in Coulombs. Current is the rate at which this charge moves or flows past a point, measured in Amperes (Coulombs per second).

Although the individual electrons have a high random speed, their net forward movement (drift velocity) is slow because they frequently collide with the lattice ions. However, there are so many free electrons (high number density, 'n') that even a slow net drift results in a substantial current.

An ammeter measures current by detecting the flow of charge through itself. To ensure it measures the total current flowing in a specific part of a circuit, it must always be connected in series with the component. Ideally, an ammeter has zero internal resistance to avoid affecting the circuit's current.