Chapter 12

This chapter reveals the fact that magnetism and electricity are in close relation. The electricity can generate magnetism, and so does the reverse.

Scientists now believe in the modern atom theory which explains the nature of magnetism plausibly. As we all know, there are lots of electrons revolve around the nucleus. We can loosely say that these electrons spin in two directions which are clockwise and counterclockwise. The electron spin cause magnetism, but the amount of electrons rotating in one direction is usually the same as that of the other; therefore, the magnetic effect is neutralized. However, in elements, such as iron and nickel, there is a significant surplus of electrons spinning in one direction over the other; thus the atoms reveal the magnetic behavior. When all of the atoms in the iron bar are arranged in order, that means they face in one direction, the bar becomes a magnet. That iron bars are not magnetic is because the atoms in the bars are in disorder. They neutralize each other’s magnetism.

The generator is invented with the underlying idea that magnetism and electricity are interchangeable. If you thrust magnet into the coil, you will discover that electricity flow in one way through the wire. When you pull the magnet out, you will find the flowing electricity again, yet in the opposite direction. If you continue to move the magnet back and forth over the coil, an alternating current will be produced. The above basic principle applies to generator. I will take hydroelectricity energy as an example. The rush of falling water spins turbines that turn huge coils of wire near giant magnets, which generates electricity.

A great use of magnetism and electricity is the invention of telephone. There are two important parts of the telephone which are the transmitter and the receiver. Inside the transmitter there is a little filled with thousands of grains of black carbon. These grains are part of the electric circuit. When you speak, your voice cause the vibration of these grains to be compressed. The squeezed grains have lower electricity resistance. On the other hand, when you stop speaking, these grains spring apart, and the electricity resistance increased. The change of resistance results in the impulse of electricity flow. The impulse causes the disk in the receiver to vibrate, which generate sound.

By using magnetism and electricity, scientists invented many practical things. Lots of new powerful machines will come out because of the application of magnetism and electricity.