Current

In the context of electricity, the flow of electrons through a circuit is referred to as an electric current. It is measured as the rate of flow of negative charge through a point. Electrons are negatively charged, thus they flow from relatively negatively charged points (excess electrons) to positively charged ones (fewer electrons). By convention, an electric current is considered to flow from relatively positive charged points to relatively negative charged points. Thus, the flow of current is considered to be in the opposite direction to the flow of electrons.

The standard unit of electric current is the ampere (symbol: A), which is the flow of electric charge (unit: Coulomb) across a surface at the rate of one coulomb per second. Electric current is measured using a device called an ammeter.

Alternating and Direct Current

Electric current can be either direct or alternating. In direct current (DC), electrons flow in the same direction at all points in time, while in alternating current (AC), the flow of electrons reverses direction periodically.

Both AC and DC generators produce currents via electromagnetic induction. In AC generators, the coil through which the current flows is a fixed point, and the magnet is moving one. The magnet’s north and south poles cause the current to flow in opposite directions, producing an alternating current. With DC generators, the coil through which the current flows rotates in a fixed field.

Electricity delivered to our homes and offices is an alternating current. Some appliances use AC, but some, especially electronic devices, need to convert the AC to DC first. Electricity is generated via electrochemical reactions as a battery, which always supports direct current (DC). There are some advantages to both AC and DC, and depending on the requirement, and the right option is chosen by both power suppliers and appliances or device manufacturers.