Conductors and insulators

Electricity, useful for so many things. When electricity runs through the cable in this string light, it reaches the bulbs and lights them up. Don't worry, Phillip, the electricity won't hurt you, even though you're holding the cable in your hand. Sure, electricity can be dangerous. But look at the cable.

You only touch the plastic on the outside. There are wires inside the cable made of the metal, copper. And it's through these that the electrical charge flows. The electrical charge loves materials like copper, because it can move fast and easily through them. Copper conducts electricity.

It's a conductor. Plastics are different. Plastics don't allow the electricity to get through. They insulate you from it so you won't get electrocuted. Plastics are good insulators.

What makes copper a conductor, while plastics are insulators? Let's back up. Electricity is all about charges, and a charge can be positive or negative. Charged particles always strive to be in balance, so that there is just as much positive as negative charge at every location. And when they are not in balance, they yearn intensively to be so.

This attraction between negative and positive charges is an electrostatic force that pulls the charged particles. An electron is a charged particle with a negative charge, and when talking about electricity, the electron is the charged particle we deal with most. The area to the left has a negative charge. It has an excess of electrons, and to the right is an area with a positive charge, a deficit of electrons, leaving the positively charged protons in the majority. The protons are attracted by the electrons, but they're stuck in their atoms, and can't move.

The electrons, on the other hand, feel the presence of the protons, and yearn to get there. These electrons are not as firmly attached to their atoms, so they can move around. But they don't get very far, because there's thin air in between, and it's too far for them to jump. So, we'll give them a hand and connect a wire, a conductor made of copper. The element, copper, has a particularly handy property.

An atom of copper has 29 electrons. Twenty-eight of them are stuck firmly in the atom, but one of them can move around freely. This free electron jumps around, and can switch places with other free electrons, circling around other atoms of copper in the wire. And these free electrons make copper capable of conducting electric current. In all conductors, electrons can move freely.

Okay, those were conductors. Now, let's swap the copper conductor for a string of plastic instead. Most types of plastic have no or almost no free electrons at all. The molecules in the plastic hold on tight to all their electrons. So no matter how much the electrons yearn to get across, nothing happens at all.

Plastics are insulators, because the electrons in the plastics are not free to move around. Most metals have free electrons and are good conductors- silver, copper, gold, aluminium, iron. While plastics, glass, and ceramics are good insulators, they conduct almost no current at all. That's what makes them safe to hold the cable even when there's current running on the inside. No, don't cut that.

Yes, this string of lights is a bit too long, but if you cut it with those pliers, you'll cut right through the plastic insulation. And the pliers, which are made of metal, will come into contact with the copper wires. Then where do you think the electric current will go? That's right, it will run right through you if you're unlucky. Yes, much better.