Electric windmill : EF 152 By: Brandon Irby, Corey Young, John Mullen, Mitchell Reiger

Device Design Basic Materials: Plastic Cup 36 Gauge Magnetic Wire Various Types of Wood Razor Scooter Bearings Four Ceramic Magnets An Assortment of Nails, Screws, and Electrical Tape

Device Design Propeller type blades are used, causing the fan to initially rotate slowly but pickup speed throughout, eventually reaching a top speed of rotation. The shaft of the blade is placed inside a bearing, which is held in place by a piece of wood. On the shaft a square block, wherein the magnets are implanted, is attached. This component is surrounded by a magnetic wire coil creating the closed circuit necessary to light the light bulb. The far end of the shaft is gently resting on top of another piece of wood rather than inside, reducing friction and greatly increasing rpm’s.

Mechancial to Electrical Energy The fan blade spins at a very fast rate. The rotational energy created by the spinning blade is translated to the spinning magnets. The spinning magnets create an electrical current within the wire. In order to produce an AC current, the magnetic field must alternate quickly from North to South or vice versa. Meaning that the magnets must be arranged carefully.

Efficiency Friction causes the largest amount of energy loss in the windmill. F f = μ k N (during rotation) with mass of shaft and magnets =0.52(0.75kg)(9.81 m/s 2 ) = 3.82 N

Efficiency 1/2 Iω 2 = U e + E loss (shaft treated as slender rod with magnets are point masses with no friction) 1/2(0.70 kg)(.01m) 2 (6 rad/s) 2 + E loss = 0.9 Volts E loss J E out = [(0.9 V) 2 /(5.4 Ω)] (5 seconds) (time bulb stayed lit with resistance of wire) = 0.75 J E in = 3.82(2π(0.02m))(60 rev) = 29.7 J (times it turned in 5 seconds) Eff = [0.75/29.7] x 100% = 2.53%

Construction Issues One major problem was thieves. Magnets, wood, electrical tape, and even an entire spool of wire mysteriously went missing. The next major problem was arranging the magnets and coil in order to create AC current. Trial and error was imposed to solve this.

Conclusions Overall, the project was fun and challenging. It required us to plan and work together in order to get everything done on time. Also, the project tested our ability to apply concepts covered in class.