Electricity

Think of the many uses of electricity. We light and heat our homes with it. We cook with it. It brings us information and entertainment. It drives our computers and factories. It starts our cars and powers our portable stereos. We rely on electrical power to live and to make living more convenient and worthwhile.

In all the years that you have been using electrical power, have you stopped to consider what electricity actually is? Let's take a look.

Electrons are the Key

Electricity is simply the flow of electrons. An electron is a tiny particle which is a part of the atom. Electrons carry a negative charge, which is the opposite of a positive charge. Since opposite charges attract, electrons are attracted by positive charges. An atom also contains particles with a positive charge, called protons, and these particles attract the electrons and hold them in place in the atom.

Figure 2.1

The atoms of some materials, such as glass, attract their electrons firmly; other atoms, such as copper, only have a loose hold on their electrons. Atoms have an equal number of electrons and protons, which results in their carrying a neutral charge, as shown in Figure 2.1.

Figure 2.2

However, if an atom loses an electron, it then carries a positive charge. If this positively charged atom were near another atom which had a loose hold on its electrons, what do you think would happen? Take a look at Figure 2.2.

As you can see, the atom at the left with the positive charge attracts one of the electrons from the adjacent atom. If the attraction is strong enough, the electron is torn away from its atom and flows toward the positive charge. Now look at the result in Figure 2.3.

Figure 2.3

The atom on the left has an equal number of electrons and protons, so it has a neutral charge. The atom in the middle, however, has lost an electron, so it now has a positive charge. It is capable of attracting a new electron from the atom on the right.

In Figure 2.4, a copper bar (which as you know is composed of atoms having loosely-held electrons) is connected to a battery (which is positively charged at one end and negatively charged at the other). Notice that the switch is open.

Figure 2.4

Because opposite charges attract, the negatively charged electrons in the copper bar are attracted to the positive end of the battery. Since like charges repel each other, these same electrons are repelled by the negative end of the battery.

As you can see in Figure 2.5 with the switch closed, the atoms in the copper bar near the positive end of the battery will lose electrons, causing them to become positively charged. This is because the number of protons has not changed.

Figure 2.5

These positively charged atoms in the copper bar will attract electrons from nearby atoms, which will then also become positively charged and attract electrons also. Remember that the electrons at the negative end of the battery are being repelled by the negative charge.

The combination of the simultaneous attraction of electrons at one end and the repulsion at the other end of the copper bar causes electrons to flow from atom to atom. This flow is shown in Figure 2.6.

Figure 2.6

Consider this question: What happens to the electrons at the positive end of the battery, which were torn away from the nearby atoms?

The answer is very simple. They flow through the battery to its negative end, where they are attracted by the positively-charged atoms that are closest to that end of the bar.

This continual flow of electrons through the bar and the battery is electric current.