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Reactance & Impedance
Transcript of Reactance & Impedance
In an AC circuit we know the voltage is sinusoidal, and that the charge built up on the plates will be
and that the current is the time derivative of this
This instantaneous current can give a peak current
We call this Capacitive reactance
This looks very familiar to Ohm's law, with a different resistance, coming from the capacitor.
following the same appoach as the capacitor we can look at an inductor circuit.
The potential across an inductor is related to the changing current
Solving for that instantaneous current via integration
The peak current then is
And using Ohms law again solves for what we call teh Inductive reactance.
In an LCR circuit there is resistance as well as both of these reactance. The three together is called impedance.
Using Ohms law you can then solve for the total current.
A series RLC circuit consists of a 25 Ohm resistor, a 5.5 mH inductors and a 275 nF capacitor. Find the impedance, peak current and phase angle, if connected to a 5000 Hz oscillator with a peak voltage of 2.5 V.
Also useful is the phase angle, from the phasor diagram