Thread: DC to AC
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Jimmy
#7
Dec26-03, 02:37 PM
P: 665
A tank circuit will not convert a direct current to AC. If you connected a tank circuit to a DC source, the inductor, if no resistor was in series with it, would short the DC source. If you did have a resistor to limit the current through the coil, then you would simply have a direct current flowing through the coil. No current would flow through the capacitive branch when the capacitor is fully charged. Effectively, with direct current, an inductor has 0 reactance and a capacitor has infinite reactance.

Inductive Reactance
[tex]X_l=2\pi fl[/tex]

Capacitive Reactance
[tex]X_c=\frac{1}{2 \pi fc}[/tex]

Both of these are measured in ohms.

When dealing with RCL circuits, the total impedance is given by:
[tex]Z=\sqrt{R^2+X_t^2}[/tex]

[tex]X_t=X_l-X_c[/tex]

At the resonant frequency,
[tex]f_r=\frac{1}{2\pi\sqrt{LC}}[/tex]

the total reactance is 0 and this means in a series RCL circuit that the total impedance is at it's lowest.

A parallel RCL circuit operating at the resonant frequency will have maximum impedance.

The frequency of a DC signal is 0 Hz so reactance doesn't come into play. Now if you're talking about pulsating DC, that's a different matter all together.