When a blackout occurs, a dysfunctional transformer is often to blame. You encounter transformers on a daily basis. They are attached to power lines, along most roads and are also inside your everyday devices. Without transformers, our homes would not be able to support electricity, because transformers convert electricity to the level our households can handle.
The first transformer was invented by Nikola Tesla in the 1889. He called his circuit the Tesla coil. It worked by converting high-level electricity into low-level electricity through a primary and secondary coil.
Modern-day transformers are cylindrical objects that sit atop power lines. You'll notice that these transformers have several cables running off them, which run into various nearby buildings.
A transformer's purpose is to convert an electrical current from high to low, and vice versa. From power lines, the electrical current feeds into the transformer at a high voltage. But the transformer reduces the voltage before transmitting it into homes.
A transformer contains a primary wire that receives the electrical current and induces electricity in a secondary wire through electromagnetic induction (inducing electricity through a magnetic field). A transformer reduces voltage when the second wire has fewer turns than the first wire, and steps up voltage when the second wire has more turns than the first wire.
The transformer you see on telephone poles is the most visible type of transformer. There are also much smaller transformers you don't see contained in devices such as laptop computers and MP3 players.
Transformers allow us to safely use our household appliances and devices because they lower the thousands of volts that come from power plants to the hundreds of volts used by our electrical devices.
Transformers that power commercial buildings and industrial centers often do not reduce the voltage quite as much. A transformer that powers a factory may not reduce voltage at all, since a factory contains huge machines that need high voltage.