|MadSci Network: Engineering|
Hi Erin, That's a great question! You could try and build a generator using magnets and a coils of wire, but it probably won't generate a lot of power. In order to make a good generator, you need good magnetic flux coupling, which can be done with commonly available materials, but it's a fair amount of work. There's a much simpler solution: use a motor in reverse. Motors and generators are very similar. Motors convert electrical energy into mechanical energy and generators do the reverse. Because of this duality, their construction is very similar. Of course, many of the design parameters are different, but the principles are the same. Here is some information on motors and generators: http://en.wikipedia.org/wiki/Electric_motor http://en.wikipedia.org/wiki/Electrical_generator So how do you do it? Get a hold of a permanent magnet DC motor and drive the shaft using wind or water. Electric power will be available at the motor terminals. You can find DC motors in toys, discarded consumer electronics such as tape players, VCRs and so on. You can purchase higher quality motors from online distributors, but I'm sure you can find plenty of motors if you look around. The Mabuchi motor company manufactures most of the motors used in toys and consumer electronics. You can find engineering data on these motors here: http://www.mabuchi-motor.co.jp/en_US/product/p_0302.html Driving the motor shaft will take a little creativity, but you should be able to come up with something that works. If you want to use wind power, find a propellor from a toy plane and attach it to the motor shaft. You can come up with something similar for a water drive. I would start with wind drive, it's not as messy. You can use a hair drier to drive your propellor and use flowing tap water for water drive. If you get the motor shaft turning fast enough, you should be able to power a small light bulb from a common flash light. You can try small single bulbs from discarded Christmas tree lights. What would happen if you connect the motor terminals to the terminals of another motor? You can try some simple experiments, such as observing the drag on the motor shaft if you connect a light bulb or short circuit the terminals. You can measure the output voltage using a voltmeter to see how the voltage changes with shaft speed. If you can get the engineering data for a specific motor, you can calculate the expected output voltage and current given the shaft rotational speed. This can be a fun project because you can see how a power station works. Power stations are bigger and more efficient, but the principles are the same. Good luck! Madhu - blog
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