What is electricity?

Electricity is a form of usable energy that can be used to power up different electronic devices or used to convert other energy forms, such as heat or mechanical energy. Electricity is considered to be a secondary energy source as it is produced from primary energy sources, like fossil fuels, wind or solar energy [see the article “How to generate electricity”]. Electricity is also used to transport energy to greater distances with low energy losses, which cannot be done with mechanical energy or heat.

In order to learn the working principles of electricity, we need to understand what an electron is. Electrons are very small (around 53.5 billion times smaller than a grain of cooking salt), negatively charged particles, which make up all of the atoms in the universe. In regards to electricity, the electrons on the outer layer of the atom (so called valence electrons) are especially important. They can in certain cases, detach from the atom structure and move to another atom. The movement of these electrons in an orderly manner is defined as the electric current (electricity). Electric current can be direct (DC) or alternate (AC).

As was explained above, the electric current needs valence electrons to move. Different materials have different electron mobility. This means that in some materials it is more difficult to make the electrons move.

Materials with very mobile electrons are called conductors (as they can conduct electricity). Most of the conductors are metals such as aluminium, copper, silver or gold. These metals are most commonly used in electrical wiring. Graphite, concrete and lemon juice are also very good conductors. On the other hand, there are materials in which it is very difficult to make the electrons move. These are known as insulators. The best insulators are inter alia: rubber, air, ceramics, plastics, dry wood or glass.

In order to make the current flow, we need some circuitry. As was discussed in the previous paragraph, the circuitry needs to be made out of conductors. For industrial use, the most commonly used conductors are aluminium and copper wires. In addition, the circuit (connection) needs to be a closed loop. The most basic electric circuit consists of an electricity source (e.g. battery, electrical generator), conductive wires, and a device to power up household appliances connected to each other. In the example below, the electricity source is a battery, that is connected to the electrical appliance (lightbulb) using conductor wires. When the connection loop is closed, the electrical current runs from the electricity source to the lighbulb powering it up.