- #1
eng_stud
- 14
- 0
Hi!
Bear with me:
When the frequency is low in an RC series circuit and we take the voltage across the capacitor, the capacitors reactance is high and thus most voltage is across it. But when the frequency is high, the reactance goes down, and little to no voltage is dropped across the capacitor.
I'm pretty much fine with the above. But, when the frequency is low, and most voltage is shared across the capacitor, the phase angle of the system is also low (towards 0 degrees). And when the frequency is high, the phase shift tends towards 90 degrees. This is what I don't get. Isn't there always a phase shift of 90 degrees across a capacitor? Or are we then talking about a 90 degree phase shift between current and voltage in a capacitor, while in this context (RC filters), we're talking about a phase shift of the output voltage vs the input voltage, and don't really care about the phase shift between output voltage and current? Are these two separate phase shifts??
Lastly: isn't it problematic that the phase voltage shifts as frequency shifts? Won't that "distort" the output in some way?
Confusing! :P
Bear with me:
When the frequency is low in an RC series circuit and we take the voltage across the capacitor, the capacitors reactance is high and thus most voltage is across it. But when the frequency is high, the reactance goes down, and little to no voltage is dropped across the capacitor.
I'm pretty much fine with the above. But, when the frequency is low, and most voltage is shared across the capacitor, the phase angle of the system is also low (towards 0 degrees). And when the frequency is high, the phase shift tends towards 90 degrees. This is what I don't get. Isn't there always a phase shift of 90 degrees across a capacitor? Or are we then talking about a 90 degree phase shift between current and voltage in a capacitor, while in this context (RC filters), we're talking about a phase shift of the output voltage vs the input voltage, and don't really care about the phase shift between output voltage and current? Are these two separate phase shifts??
Lastly: isn't it problematic that the phase voltage shifts as frequency shifts? Won't that "distort" the output in some way?
Confusing! :P