Wayne Fox, age 13, of Montgomery, for his question:
WHAT DOES A TRANSFORMER DO?
A transformer is a device that increases or decreases the voltage of alternating current. It enables power companies to transmit electric power with low amperages and high voltages without increasing the size of the wires.
To move electricity through power lines more efficiently, it is desirable to have electricity at a high voltage. This is accomplished by the use of a step up transformer.
Home appliances, lights 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 accomplished by the use of a step down transformer.
The typical transformer consists 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 source 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 as though it were a magnet. This 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 the 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 voltage of 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 one half as many turns, the induced voltage will be one half as much.
Transformers are usd in lighting, in the transmission of power, in radio and in many other electrical circuits.
There are many types of transformers, according to their uses. One type is known as an air core transformer because it does not have an iron core. Another type has a core made of powdered compressed iron. In each case where the transformer is used, it provides a quick and inexpensive way of transferring electrical energy from one circuit to another.