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L1, Introduction

The word electronics is derived from "electron." Electrons are sub-atomic particles with a negative charge. The unit for electric charge is the coulomb. One coulomb equals the charges of 6.24 x 1018 or 6.24 quintillion electrons. A single electron has a charge that is too small to measure in most electronic devices, so scientists use coulombs as a more useful way to describe charge,

Electron a tiny particle which forms part of all atoms, which, as everybody knows, make up everything in the world. Atoms contain other types of particles - protons and neutrons - but it is the electrons which will be interesting us here.

Electrons and protons have the electrical property of charge. Protons have positive charge and electrons have negative charge and they normally balance each other out. We don't really need to know what charge is. It's just a property like weight or color, but it is this property which makes the whole of electronics happen. But keep in mind the fact that opposite charges attract and similar charges repel.

When electrons move together in a unified way we say there is a current flowing. Electrons are actually moving all the time in materials like metals but moving in a random disordered way. A current is when they all move together in one particular direction.

When you touch a lift button having walked across a synthetic carpet and you feel a shock, that is electrons flowing through you to the ground. That's all a current is, simply the movement of electrons in a particular direction.

Electrons can't flow through every material. Materials that allow a current to flow easily are called conductors. Materials that don't allow a current to flow are called non-conductors or insulators. Metals are the most common conductors. Plastics are typical insulators.

Conductors- Gold, copper, carbon etc.

Non-conductors- Plastic, wood, air etc.

A battery supplies the 'force' that makes the electrons move. This force is called the voltage. The bigger the voltage the more force. Mains electricity which is 240 volts is more powerful than an ordinary 9 volt battery.

Currents are measured in amps, and voltages are measured in volts (after the scientists Ampère and Volta). Voltages are sometimes called potential differences, or electromotive forces, but we won't use these terms here.

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