From the Power Plant to Your Socket

What you'll learn

• Most power plants have a generator: a big magnet spinning inside copper coils. Steam (from coal, gas or a nuclear reactor), falling water or the wind turns it. Solar panels are the exception — nothing spins.
• The spinning magnet pushes electrons one way, then back: alternating current (AC). 50 cycles a second in India, the UK and Europe; 60 in the USA and Canada.
• A big generator makes about 11,000–25,000 V. A step-up transformer raises it to about 110,000–765,000 V for the long-distance lines.
• A transformer = two coils on one iron core. More turns on the output coil → more volts (3× the turns → 3× the volts).
• Same power = volts × amps: 10,000 V × 100 A = 100,000 V × 10 A. The heat lost in a wire grows with the current squared, so 10× less current = 100× less heat. That's why the big lines use such high voltage.
• A substation steps it down for the local lines (about 11,000 V in India / UK / Europe, about 4,000–35,000 V in the USA), then a transformer on a pole or in a street box gives 230 V (120 V in the USA and Canada).
• The wires store nothing: power plants make your power the very moment you use it.