Benjamin Franklin was an inventor. He lived in the 1700s. He was very interested in electricity. He thought lightning was electricity, but he wanted to find out for sure.

There is a very well known story about Benjamin Franklin and lightning. People say that he flew a kite during a thunderstorm. The kite had a metal key attached to it and lightning struck the key, Franklin knew the lightning was made of electricity because he knew that metal is an excellent conductor of electricity. The story goes that Franklin experienced a shock from the key.

Actually we know that Franklin could not have been holding the kite or been near to it because he would probably have been killed when the lightning struck the key. The electricity would have flown through his body and caused very serious injury – so this experiment is not one that anyone should try to repeat!

We do not know exactly how Franklin made his discovery about lightning being electricity. We do know that his invention of the lightning rod has saved many lives. A lightning rod is a long metal strip that is attached to a corner of a building. When lightning strikes the building, it flows to the ground through the rod instead of into the building.

Electricity is composed of electrons:

Electricity is composed of very tiny objects called electrons that are moving very rapidly. Electrons are one of the types of particles that make up tiny objects called atoms. There is still much that we don’t know about the nature of electrons – hundreds of scientists spend their lives finding out more about electrons. Atoms are so tiny that we cannot see them with our eyes, but only with very powerful microscopes. Just as bricks are the building blocks for houses, atoms are the building blocks for everything that we can touch, hear, smell, see and taste.

Electrons are part of Atoms:

Look at the picture of the atom at right. (Inside an atom, electrons circle a nucleus).

In the center of the atom is another particle called the nucleus. Electrons occupy the rest of the space of the atom and are outside the nucleus, moving rapidly, so rapidly that when we imagine them, we think of a “cloud” of electrons around the nucleus. The nucleus contains two types of particles. These are called protons and neutrons.

If we wish to understand the nature of electricity and atoms and electrons better, we need to know that objects can have electric charge. Just as objects can have different colors and different smells, they can also have different charges. If you have long hair, you may have noticed that your hair lifts away from your head when you brush it. This is because each hair has gathered a charge. Objects can be positively charged or negatively charged, or have no charge. When an object has no charge, we say that it is neutral. Electrons have negative charge, protons have positive charge and neutrons are neutral.

The nucleus of the atom holds tightly to its protons and neutrons. However, the electrons are loosely held in most atoms. They can move easily from one atom to another.

Electricity & Static Electricity:

Think about clothes tumbling in the dryer. Electrons from some clothing rub off onto other clothing. A sock may pick up extra electrons from a towel. The extra electrons give the sock a negative charge. Meanwhile, the towel has given away some of its electrons. Now it has a positive charge.

Positive and negative things are attracted to each other. This is why the sock and towel stick together.

Things that have the same charge repel each other. This means two things with a positive charge push away from each other. Two negative things also push away from each other. When we brush our hair, each strand of hair has the same charge, the strands of hair repel each other and so push away from each other.

Conductors and insulators:

Materials that allow electricity to flow through them easily are called electrical conductors. Most metals are good conductors.

Electricity is energy. When it travels, energy moves from one place to another. If electricity can flow through a kind of matter, then that matter is called a conductor. Most metals are good conductors.

If electricity cannot flow through something, then that thing is called an insulator. The atoms of an insulator hold on tightly to their electrons. Few electrons can flow through. Air, paper, wood, and plastic are insulators.

Electricity and energy:

To understand electricity, we need to be able to understand some ideas about the word "energy". This can be a tough word to understand when we are thinking about science. This is because we use the word energy outside science to describe how we feel. When we are tired, we say we have no energy and when we are doing lots of things, we say we are full of energy. In science we use to term energy to talk about what we need to change something. We need energy to make something hot. We need energy to move something. We need energy to make a light shine. Electricity is one form of energy and can be used to make something hot, to make something shine and to make something move.

Electric Circuit

You need three things to build an electric circuit. You need a source of electrical energy, such as a battery, a conductor, and something to receive the energy. When connected to each other in the correct order, these things make up a circuit. We will learn more about circuits in the next section.

Video Instruction
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• Introduction to Electricity [5:16]

• Principles of Electricity (1945) - Part 1 [10:46]

Now let's do Practice Exercise 1-1 (top). Choose printer friendly or online exercises. Printer friendly version requires the Adobe Acrobat Reader 5. Click HERE to obtain a free copy.