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13: Alternating Current

Last updated

Mar 5, 2022
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- 12.8: Ferrimagnetism
- 13.1: Alternating current in an inductance

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Topic hierarchy

13.1: Alternating current in an inductance
When a current is passed through an inductor, as a consequence of the inductance, a back EMF will be induced.
13.2: Alternating Voltage across a Capacitor
At any time, the charge Q on the capacitor is related to the potential difference V across it by Q=CV. If an alternating voltage is applied across the capacitor, then the current and voltage are out of phase, and that V lags behind I by 90°,
13.3: Complex Numbers
I am now going to repeat the analyses of Sections 13.1 and 13.2 using the notation of complex numbers. In the context of alternating current theory, the imaginary unit is customarily given the symbol jj rather than ii , so that the symbol ii is available, if need be, for electric currents.
13.4: Resistance and Inductance in Series
The impedance is just the sum of the resistance of the resistor and the impedance of the inductor.
13.5: Resistance and Capacitance in Series
The impedance of a resistance and a capacitance shows that the voltage lags behind the current.
13.6: Admittance
In general, the impedance of a circuit is partly resistive and partly reactive. The real part is the resistance, and the imaginary part is the reactance. The reciprocal of the impedance Z is the admittance, Y .
13.7: The RLC Series Acceptor Circuit
13.8: The RLC Parallel Rejector Circuit
For the RLC Parallel Rejector Circuit, the magnitude of the admittance is least for certain values of the parameters. When you tune a radio set, you are changing the overlap area (and hence the capacitance) of the plates of a variable air-spaced capacitor so that the admittance is a minimum for a given frequency, so as to ensure the highest potential difference across the circuit.
13.9: AC Bridges
13.10: The Transformer
In a transformer, the EMF induced in the secondary coil is equal to the number of turns in the secondary coil times the rate of change of magnetic flux; and the flux is proportional to the EMF applied to the primary times the number of turns in the primary.
13.11: Root-mean-square values, power and impedance matching

Thumbnail: A graph of voltage and current versus time for 60-Hz AC power. The voltage and current are sinusoidal and are in phase for a simple resistance circuit. The frequencies and peak voltages of AC sources differ greatly. (CC BY-SA 3.0; OpenStax).

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