OK, so we need transformers to change the high voltage to low voltage for our homes. Why don't they just use low voltage electricity in the powerlines?
Excellent! One of the wonderful things about alternating current (the electricity you get from a wall outlet) is that you can use a transformer to alter the voltage and amperage. Amperage basically tells you how much electricity (actually how many electrons are passing a point per second), while voltage basically tells you how hard those electrons are being pushed.
When electricity flows through a wire, electrical resistance changes some of the energy into heat. The higher the amperage, the more energy you lose to heat. Too much heat causes the wires to melt.
Luckily, we can use transformers at the power plant to give us very high voltage, low amperage electricity, so it can be transmitted long distances without too much energy loss, and without burning up the wires. For the main lines, the voltage can be more than 500,000 volts. Substations have transformers that step the voltage down some, increasing the amperage, and then the pole transformer steps the voltage down again, to either 120 volts or 240 volts, depending on where you live. That increases the amperage too, giving us the right amount of power for our appliances.
As for the 120 volts in the US, it is due to economics. When electricity was first available to homes, it was used only for lighting. At the time, 120 volts was optimum for light bulbs, so that was the voltage that was used. Sixty cycles per second was the most efficient frequency for powering electric motors in factories, so that was also adopted.
As use of electricity spread to other countries, it was found that you could use smaller wires if you used higher voltages, so Europe adopted 240 volts, letting them save money on powerlines. One price that they pay is that their incandescent bulbs have thinner filaments, and burn out more easily. AEG in Germany felt that 50 cycles per second was better, and set up their system using that.
Once the systems were in place, it was just too expensive to change them. Imagine if the government suddenly told everyone that they had to replace every electrical device in their house because they were switching systems.
nice explanation of amperage/voltage
Hey, that was a great simple explanation. I've always compared these to an interstate--amperage is how many cars are going by, voltage is their speed.
Anyway, I have a comment to your last suggestion. The government may not be telling us that we need to switch to a different current set up, but it is trying to make us feel that incandescent light bulbs are somehow "evil" and as I understand it, they will soon be outlawed and unavailable to buy. Fluorescent light is certainly cheaper, but I don't see how, since you can't just throw them away, they are really any "greener". (It is my understanding that there are considerable health risks for fluorescent making factory workers too.) So, it's my opinion that the government is trying to make us accept demands. Interesting that this came up--at least to me!
Respose from morgan
Hi Mr. Krampf,
Why is there a woodpecker there?? I would think that they don't use low electricity because the power travels a lot!!!
Your Admirer,
Morgan
Hi Morgan, The woodpecker was
Hi Morgan,
The woodpecker was the original reason that I took the photo. It was pecking on the pole to make the BRRRRRRRR sound that many woodpeckers use as part of their song, to stake out territory.
Low voltage?
I agree with Guy, I think that if the current was weak that the power would dwindle out over the long distance it has to travel. (and because of resistance.) Also these wires power many things like factories and such that need quite a bit of power and if it was weak that wouldn't work.
L. Albers
physics time!
Power is equal to the voltage (V) times the current (I).
If you decrease the voltage, you have to increase the current to maintain the same amount of power.
However, the heat dissipated in a circuit is I²R. The resistance in a circuit is R=V/I. Therefore, a high resistance means a high voltage.
So it is more efficient to send out power at a high voltage, because the heat dissipated increases by I² for current, as opposed to R for resistance.
Hmm,...
Well, I think it's because mabey the high voltage is needed for the businesses and the shops??? Or like the below, mabey the wires feed alot of houses???
Just a thought! :P
Jazzy.
Power Lines
We believe there is resistance in the wires that can affect the flow of electrical current. The longer the distance, the less power is received at the other end, The step down transformer insures that every location receives the same voltage to power all of our 120v devices. Too much power would fry them, while too little power would not be enough.
Power loss is why
Power is Volts * Amps
P = V * I
Voltage can be found as the Amps running thru some resistance.
V = I * R
Substituting we get
P = I * R * I
or
P = I^2 * R
Since almost everything has some resistance to the flow electricity, the only 2 ways to lose less power, are to reduce the resistance, or reduce the current. I can reduce the current by raising the voltage, or I can reduce the resistance by changing the type of wire. In some instances http://www.treehugger.com/files/2008/05/superconducting-cables-save-ener... , they have done just that replacing ordinary transmission lines with superconducting ones, wires that have far less resistance than the ones hanging in most neighborhoods.
Since P = V * I, if I double the voltage, I have halved the current. In many instances, the voltage may be more than 30 times higher on the transmission lines (those on the poles) than the delivery lines (those connected to the house), so the current is much less than it would have been otherwise.
Also, the loss of power due to resistance, comes in the form of heat, which can melt the wires or reduce their strength, causing them to fail under heavy load, since more current means more heat.
Another way to reduce the amount of resistance, is to shorten the length of the wires. you can do that by generating the power in your own backyard, using wind or solar like this http://www.gadgetgrid.com/2007/03/26/10000-kw-electrical-power-generatio... .
Why don't they just use low voltage electricity in the powerline
U=I*R ?
i think
i think because that the power lines are going for a long distance, and these wires have some kind of resistance.
or maybe because these wires feeds a lots of houses... or something like that :)
Guy,Israel
high power on lines
U=IxR ?
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