Jim Teason, age 12, of Flagstaff, Ariz., for his question:
HOW DOES A TRANSFORMER WORK?
A transformer is a piece of equipment that increases or decreases the voltage of alternating current. It allows power companies to transmit electric power with low amperages and high voltages without increasing the size of the wires.
It is desirable to have electricity at a high voltage because this way it moves more efficiently through power lines. This is accomplished by the use of a step up transformer.
Home appliances, light and electrical machinery need much less power than is driven through power lines. In this case, it is more practical to use low voltage. This is achieved by the use of a step down transformer.
A transformer is made up of a hollow iron core and two coils of wire. The iron core is shaped like a square. Around one side of the core is wound a wire which is known as the primary coil.
Another coil is wound around the other side of the core or around the first coil, and is known as the secondary coil. The two ends of the primary coil are connected to the sources of voltage that is to be changed, such as a generator.
The secondary coil is connected to the circuit to which the electricity is to be transferred. As the alternating current goes through the primary coil, it sets up a magnetic field, much the same as though it were a magnet.
The magnetic field consists of lines of force that change in number and direction. These lines cut through the turns of the secondary coil, which sets up an alternating current in this coil. The current through the secondary coil is known as the induced current and its voltage is known as induced voltage.
If the number of turns in the secondary coil equals the number of turns in the primary coil, the induced voltage will be the same as the primary coil.
If the number of turns in the secondary coil is greater than that in the primary coil, the induced voltage will be increased. Similarly, if the number of turns in the secondary coil is less than that of the primary coil, the induced voltage will be lessened.
The voltage in the secondary coil is directly proportional to the number of turns. If the secondary coil has twice as many turns as the primary coil, the induced voltage will be twice as much.
If the secondary coil has one half as many turns, the induced voltage will be one half as much.
Transformers are used in lighting, in the transmission of power, in radio and in many other electrical circuits.
There are many types of transformers. Each is designed to provide a quick and inexpensive way of transferring electrical energy from one circuit to another.