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A transformer is a machine simple in design, but sublime in its simplicity.
When I was a child, I remember looking up at the mysterious buzzing boxes perched atop power poles. I knew they were called transformers, but what did they do? The dark box hid the workings of a strange device and the name only enhanced the mystery. A transformer allows electricity to be generated in large quantity and be distributed in small amounts to millions of individual consumers. It is also one of the reasons that alternating current technology ultimately triumphed over direct current, much to the chagrin of Thomas Edison who championed the former. The transformer steps down voltage from one incoming line, and creates a smaller voltage going out. Inside the transformer is a core, usually made of iron. Around the core are two sets of wound wire. One set has many windings, the other fewer. When alternating current flows through the system, the incoming coil generates a magnetic field in the iron core. This magnetic field then induces an electric current in the second set of windings. If the incoming number of windings is greater than that outgoing, the voltage is reduced. If the incoming number of windings is less than the outgoing, the voltage is increased. The change in voltage means that there will also be a corresponding change in current, since these two properties of electricity are intimately related. The total power going into the system must equal the total power emerging from the system. Power, as it relates to electricity, is defined as the voltage multiplied by the current. So the incoming voltage times the incoming current equals the outgoing voltage times the outgoing current. If the outgoing voltage is less than the incoming voltage, then the outgoing current will be more than the incoming current. This also means that if the incoming number of windings is greater than the outgoing number the outgoing current will be greater than the incoming current. So what about the buzzing? The buzzing itself is harmless, but it is a good warning that the transformer is electrified and needs to be avoided for that reason (high tension power lines may also emit this sound). It is a side effect of the alternating current. The tone is generated when the current switches direction. As this happens, some energy is transformed into sound and is lost to the surrounding environment. This means that the device isn't entirely efficient.
The copyright of the article Transformers in Physics is owned by Katharine M. J. Osborne. Permission to republish Transformers in print or online must be granted by the author in writing.
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