Here is a quick recap from my posts about my mini motor and my unit seven summary about electromagnetic induction, which is the big physics concept at work here.
Electromagnetic induction is when a voltage is induced in a current-carrying wire by the relative motion between the coil of wire and a magnet. If a magnet moves in or over a coil of wire, or vice versa, the wire's magnetic field will align with that of the magnet. This change in magnetic field will induce a voltage, which causes current to flow. The force of the magnetic field causes a torque on the wire, which makes it spin. This is a great example of a conversion of energy from mechanical to electrical.
A pure example of this can be seen here, in the video of the motor I made. Notice how, as the wire is positioned over the magnet, the wire spins.
There are other physics concepts you should be aware of before building your own wind turbine.
Newton's 1st Law of Motion
An object in motion will remain in motion unless acted upon by an outside force and an object at rest will remain at rest unless acted upon by an outside force.
That's where friction comes into play: every piece of your turbine needs to be measured, made, and assembled with care so that haphazardly cut pieces do not rub together and cause unwanted friction. The more friction there is, the less the turbine will spin and the more poorly it will produce energy.
Newton's 2nd Law of Motion
Newton's second law of motion states that acceleration is directly proportional to force and inversely proportional to mass.
This is important when it came to the blades of the turbine. Since we tested them inside with fans, we had to make sure that our blades were lightweight in order for the wind's force to cause the turbine to accelerate.
Newton's 3rd Law of Motion
For every action, there is an equal and opposite reaction.
This is another reason for why the blades have to be made out of a lightweight material. According to Newton's 3rd Law, the blades will push the wind with the same amount of force with which the wind is pushing the blades. Therefore, heavier blades are even less likely to move.
Materials and Method
Like I did for the mini motor, my partners and I kept the materials for the wind turbine pretty basic. We used, for the most part, household items. All in all, we spent less than $15 on materials.
- cardboard-- for the base and the frame
- copper wire-- to carry the current and cause the blades to move
- cut pieces of a recycled plastic water bottle (typical vending machine fare)-- for the blades
- metal dowel-- as an axle
- wooden dowel-- to stabilize the blades
- masking and electrical tape-- to hold together the magnets and the blades
- hot glue-- to secure the frame and the base
- wooden block-- to provide a level bottom for the base
We didn't follow the instructions to a tee (read on for an explanation about our 200ft wire disaster!) but they were very helpful and I am sure you will be even more successful than we were if you do follow these instructions more carefully.
Like in the video, we placed our magnets inside the cardboard frame, attached to the metal axle. We bought the ceramic block magnets, but they caused us trouble, so we ended up using stacks of small, round magnets instead. In order for electromagnetic induction to occur, we wrapped the wire around the outside of the box. The change in magnet field caused the magnets (taped to the axle) to spin. Since the magnets were spinning, so did the axle, which is how we got our turbine blades to move.
The actual blades were built by cutting strips of plastic water bottle and taping them to a wooden dowel which would then be glued to a cardboard platform on the end of the metal axle.
Here are some images of our final turbine (it's not a work of art, I know).
In the end, we produced 0.008A and 0.005V. It worked! Unfortunately, we (unlike you because I warned you!) were not able to light an LED light bulb because there was too much friction caused by the amount of tape holding the magnets together.
Here is a video of my turbine in action. I know it's horribly pixelated, but maybe you can make out the fact that it really did spin.
In the end, I got to see the concept of more coils = more voltage in action. I'm really glad that we followed a specific design for the generator, even though we needed to tweak it a little. The ceramic block magnets ended up not working for us because once we wrapped them to the axle with tape, there was too much friction inside the frame for it to work well. Overall, I wish we had made the frame bigger, to allow us to have more flexibility with our materials. My biggest piece of advice, similar to my advice from the mousetrap car, be METICULOUS in everything. One of our biggest setbacks with this project was that we did not coil the copper wire around the frame immediately as we unspooled it. As a result, we effectively tangled 200ft of perfectly good copper wire, wasted class time and personal time trying to fix it and ended up wasted the wire we could not salvage. I think that if we had taken a little more time to think through each of our steps, we wouldn't have tangled the wire or made the frame too small.
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