EMInduction

I started with a digital code, then went to photocells/CDs, then to magnetic induction/audiotape, then back to A-D, D-A conversions.
 * Concept Summary**
 * Some materials can be permanently magnetized with an electrical current.
 * cut strips of cassette tape, magnetize them, set up a digital code, move permanent magnet by to deflect up or down.
 * demonstrate magnetizer
 * Hard drive dissection/mapping, including currents produce motion, and magnets can be shielded.
 * Moving magnets can generate electrical currents. (induction)
 * Demonstrations with magnets, multimeters, and coils.
 * Secret Life of Machines on VCRs
 * Some materials can release electrical charge when illuminated. (photoelectric effect)
 * phet simulation on conductivity
 * cadmium sulfide photocells, lasers, and multimeters
 * CD players dissected
 * mirrors, electrical tape, lasers, photocells make a barcode and reader
 * Analog codes use patterns that allow continuous variation.
 * phonograph records
 * A-D, D-A conversion worksheet
 * Digital codes use patterns that allow only discontinuous values.
 * binary numbers, ASCII code