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Q & A: A big magnet and the city of the future

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Most recent answer: 10/22/2007
Q:
I’m doing a science project on " a city in the future", and i’m thinking about powering it with electromagnetism. My idea is to place a giant magnet underground with underground wires leading to other parts of the city. will this work out?
- jonathan (age 10 1/2)
miami, FL
A:
Hi Jonathan,

That sounds like a good project to work on! We need more people to think about great ways to live in the future.

Today's cities are already largely powered by electromagnetism, with electric current passing through underground (and aboveground wires). We also use energy from burning fossil fuels, and even the electric energy we use usually can be traced back to burning fossil fuels, to using nuclear reactors, or to using renewable energy sources such as hydropower, wind power, solar power, or geothermal power.

The reason we have such a variety of energy sources today is that energy does not come for free. Energy can be changed from one form to another, but it cannot be created from nothing.

The good news is that magnetic fields store energy. You can use a big electromagnet a bit like a battery. You still have to power it up however, getting energy from some other source. A permanent magnet will also have a magnetic field, but since it doesn't change, you can't get the energy out of it. Also, the energy storage ability of a magnetic field is not very large or convenient compared to, say, the energy stored in fuels like oil or coal. And it's easier to move gasoline and coal around than to move big magnets.

But speaking of moving magnets, that's pretty much how we generate the electricity in a power plant. A big loop of wire (actually, many loops all coiled together) is turned around on an axis in a magnetic field. This procedure generates a voltage in the loop of wire, following Faraday's law of induction. The energy needed to turn the loop of wire is usually gotten from a steam turbine, and the steam is generated from burning fuel. Windmills and water turbines in rivers also do the job.

So yes, you can build the city of your dreams, but be sure to have a source of energy to keep things going!

Tom

(published on 10/22/2007)

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