The document discusses AC circuits and phasor diagrams. It introduces AC sources and defines RMS values. It describes how resistors, capacitors, and inductors behave in AC circuits, with the voltage across a resistor being in phase with current, the voltage across a capacitor lagging current, and the voltage across an inductor leading current. Kirchoff's loop equation is presented and phasors are introduced to represent instantaneous voltages, allowing the maximum voltages to be calculated even when they occur at different times. Example phasor diagrams are shown graphically.
15. I = I max sin(2 ft ) ( = 2 ft ) V L = I max X L sin(2 ft + ) V R = I max R sin(2 ft ) V C = I max X C sin(2 ft – ) Graphical representation of voltages L R C I max X L I max R I max X C
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Notes de l'éditeur
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Ave V = 0 Ave V^2: Vmax/2
Ave V = 0 Ave V^2: Vmax/2
85% and 78% correct respectively
Changing voltage tries to charge/discharge capacitor. Low frequency limit: open circuit High frequency limit: closed circuit (capacitor never has time to build up charge) Lag: charge (voltage drop) lags behind current.
Low frequency: no voltage drop…nothing is changing High frequency: large rate of change of current implies large emf (as per Faraday) Voltage leads current. (rate is initially large, current then grows as rate drops)
“ can be ignored” means “behaves like a wire”…no voltage drop
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