PHYS 132 Lecture Notes - Lecture 1: Kilowatt Hour, Electromagnetic Induction, Ammeter
14 Oct 2016
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: work done per unit charge (v = w/q) Resistance of a wire: r = l/a where a = r2. Least resistance (best conductor): short, fat, cold most resistance (worst conductor): long, skinny, hot. Voltmeter: connect in parallel, infinite internal resistance ammeter: connect in series, zero internal resistance. Adding extra resistor decreases total resistance and increases total current. Mechanical power: p = w/t = fd/t = fv electrical power: p = vi = i2r = 1 electronvolt (ev) = 1. 60 x 10-19 j. 1 kilowatt hour = (1000 w)(1 hr) = 3. 6 x 106j. Three units of energy: joules, electronvolts, kilowatt hours. Adding extra resistor increases total resistance and decreases total current. Ohmic device: follows ohm"s law (v i at constant t) = constant resistance. Non-ohmic device: resistance not constant (eg. filament lamp) Two principles of electromagnetism: 1) an electric current (or moving charged particle) generates a magnetic field. 2) a changing/moving magnetic field induces an electric current (electromagnetic induction).
