One thing you won’t be able to escape in physics is learning the makeup of an atom. I’m sorry, but it’s just something you have to know. Now we’ve got that sorted, let’s get down to the basics. As you most likely already know, an atom is made up of a central nucleus and a number of orbiting electrons. The electrons are held in orbit because they and the nucleus have opposite electrical charge. The particles in the nucleus – protons – have a positive charge. Meanwhile, the electrons have a negative charge.

The next important thing you should know is that in the event that an atom loses an electron, it becomes a positive ion. If it gains one, it becomes a negative ion. Simply put, an ion can be positive (if the atom loses an electron) or negative (if it gains one). Atoms never normally gain or lose protons because they are protected deep in the nucleus. Lucky them!

Another key thing to remember while studying atoms and electrons is that some materials allow electrons or ions to flow freely. These are known as electrical conductors as they allow charge to flow through them. The best example is metals. When the atoms bond together to form a metal, a number of free electrons are produced which can flow through the material. This means that conduction in a metal consists of just negative particles going one way.

One last thing to learn, I swear! When scientists first started talking about electricity properly they agreed that current would always be measured as the flow from the positive to the negative terminal. That means the flow of positive charge. Unfortunately in a metal, it is negative electrons moving. So now we have the term “conventional current” (or just “current”, which is the same thing) for the flow of positive charge and it is in the opposite direction to electron flow. Electrons flow from the negative terminal to the positive, but current is always from positive to negative.