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In yesterday's post we discussed how Edison and several wealthy investors electrified New York City and turned the lights on only to run into a fundamental problem; he couldn't keep the lights the same brightness. Even an office building outfitted with Edison's light bulbs had noticeably dimmer bulbs at the top of the building than at the bottom, perhaps by as much as half.

As sometimes happens with new technologies, the practicality of the invention comes into question when you try and apply it to a broad spectrum of users - and that's just what happened to Edison. His investors as well as his customers demanded a fix for this problem. Unfortunately, the problem was a fundamental one that had to do with the nature of power itself.

When you send power down a wire the ride it takes isn't free. As it is traveling down that wire it loses energy in the wire itself. The more energy you use at the end of the wire the greater the loss will be at the point you need the power. The reason for this is fundamental: the wire becomes a heater and the power along the wire is converted to heat. The more power you try and draw from the wire, the more heat is created and what's not converted to heat is what you have left to power the light bulb. The longer the wire, the greater the loss.

So Edison had no choice but to try and figure out a way around this fundamental property of electricity running through a wire - and his choices weren't many. Let's use a water analogy and picture a long main water pipe feeding many homes so you can see the problem easily. There's a certain amount of water pressure in the main pipe but as soon as any one home starts to draw water to fill a bath, some of the pressure goes to that task and the main pressure in the pipe goes down. I am sure you've seen this at your house when you're watering the garden or lawn and someone inside flushes the toilet - the water coming out of your hose goes down.

One way around this problem is to put more water pressure than any of the homes together would need and then regulate or limit how much of that pressure can be used. If you have 10 homes and each home needs 10 pounds of pressure, if the main pipe has only 10 pounds available then you have a problem. But if the pipe has, instead, 100 pounds of pressure then each home can grab its 10 pounds and none of the other homes feel any difference.

Unfortunately for Edison regulating or limiting higher main voltages doesn't work because in that day there was no way of making a specific limiter. The ability to do this wouldn't happen for another 50 years.

He was stuck, but an answer was right around the corner - although for Edison, it wasn't an answer he would be happy about.

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Paul McGowan

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