The basics of electricity

Electricity begins with the structure of matter. Atoms contain a nucleus of positively charged protons surrounded by negatively charged electrons. In some materials, called conductors, the outer electrons are loosely held and can move freely from atom to atom; metals such as copper are good conductors for this reason. In other materials, called insulators, the electrons are tightly bound and cannot move easily, so these materials block the flow of electricity. This difference is the foundation of how electrical circuits are built and controlled.

An organised flow of these free electrons is an electric current. To make charge flow, a source of energy such as a battery or generator establishes a voltage, a difference in electrical potential between two points that pushes the charge around a circuit, much as a pump creates pressure that moves water through pipes. Every conductor offers some resistance to this flow, converting part of the electrical energy into heat. These three quantities are measured in amperes, volts and ohms respectively.

For current to flow there must be a complete, unbroken loop called a circuit, leading from the source, through the components and back again. Opening the loop with a switch stops the current. Components can be connected in series, one after another so the same current passes through each, or in parallel, side by side so they share the same voltage. Understanding conductors, insulators, the three basic quantities and these two ways of connecting components provides the groundwork for all further study of electricity.

Frequently asked questions

What is the difference between a conductor and an insulator?

A conductor, such as a metal, has loosely held electrons that move freely so current passes easily, while an insulator holds its electrons tightly and blocks current.

Why must a circuit form a complete loop?

Current can only flow around an unbroken path from the source and back; if the loop is broken, for example by an open switch, the flow stops.

How do series and parallel connections differ?

In series, components are joined end to end so the same current flows through each; in parallel, they are connected side by side so they share the same voltage.