Earth's magnetic field extends into space, creating the magnetosphere. Field is generated in outer core through geodynamo process. Magnetic poles wander about 25 miles northwest annually. Magnetic poles flip approximately every 200,000-300,000 years
Electric motors convert electrical energy to mechanical energy using electromagnetic phenomena. Most motors develop torque through interaction of current conductors and magnetic field
Rotor consists of steel laminations with aluminum or copper conductors. Contains cage-like structure with bars connected by shorting rings. Core made of high-silicon iron with varnish insulation. Rotor slots must be multiples of stator slots to prevent interlocking
Bifilar coil contains two closely spaced, parallel windings. Tesla patented parallel-wound, series connected bifilar coil in 1894. Wire can be purchased as different colored enameled strands
Ampère's force law describes the attraction or repulsion between current-carrying wires. Each wire generates a magnetic field following Biot-Savart law. The other wire experiences a magnetic force following Lorentz law
First electromagnetic rotary machine built by Ányos Jedlik in 1826-27. Hippolyte Pixii created alternating current generator in 1832. Moritz Jacobi developed motor lifting 10-12 pounds at 1 foot/second in 1834