Why Does a Capacitor Block DC Voltage in a Circuit?

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A capacitor blocks DC voltage in a circuit due to its infinite impedance at zero frequency, which prevents DC current from flowing. In the discussed circuit, changes in DC offset voltage affect the waveform in channel one, while channel two, measuring voltage across a resistor, shows no DC component. This indicates that the DC voltage drop occurs entirely across the capacitor. The absence of DC current results in no voltage across the series resistor. Thus, the capacitor effectively isolates the DC component from the rest of the circuit.
mmmboh
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Hi, I have this circuit:

241.jpg




And when I change the DC offset voltage the wave in channel one moves up and down and the wave in channel 2 doesn't do anything except for flatten out a bit in certain areas (although I'm not sure that's relevant), my question is why? I know channel 2 is the voltage across the resistor, so is the change in DC voltage appearing solely across the capacitor? It appears the capacitor blocks voltage, but why?

Help would be great! :)
 
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The capacitor blocks the DC current. (Its impedance is 1/(wC) so zero frequency means infinite impedance.) No DC current, no DC voltage across the series resistor, the signal in CH2 has no DC component. The DC voltage drops solely across the capacitor, as you said.


ehild
 

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