Why Does a Capacitor Block DC Voltage in a Circuit?

[mmmboh]

Hi, I have this circuit:

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! :)

 

[ehild]

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