In the circuit below, why does the AC voltage remain constant even though the frequency increases?


  • 3
    \$\begingroup\$ Can you say more about what situation you are asking about? There's no general rule that "the ac voltage stays constant as the frequency changes". Talking about the DC voltage changing as frequency doesn't make sense, because the dc voltage is the voltage at f = 0 Hz. \$\endgroup\$
    – The Photon
    Mar 4, 2014 at 0:55
  • \$\begingroup\$ I connected a my circuit to a function generator and oscilloscope. My circuit is also connected to two resistors.I collected my AC voltage as I increase my frequency.However, I noticed that my Ac voltage did not actually change. When I reached, a frequency of 1 million, my AC voltage increased largely. \$\endgroup\$
    – eLg
    Mar 4, 2014 at 1:10
  • \$\begingroup\$ What is your circuit? You can upload an image file showing the schematic to an image hosting site, and let us know the link; someone will edit your question to include it inline. \$\endgroup\$
    – The Photon
    Mar 4, 2014 at 1:14
  • \$\begingroup\$ s30.postimg.org/40ukyunch/Capture.jpg \$\endgroup\$
    – eLg
    Mar 4, 2014 at 1:21
  • \$\begingroup\$ @eLg When you generate an AC waveform with a function generator and increase the frequency, the amplitude doesn't change. This is how function generators usually work by design. \$\endgroup\$ Mar 4, 2014 at 1:21

1 Answer 1


I can't see your circuit since the server in my university blocks the domain of the image hosting site, but based from your comment "I connected a my circuit to a function generator and oscilloscope. My circuit is also connected to two resistors," I am assuming that those are the only components in your circuit so I will base my answer on that.

Resistor is a component that is NOT frequency dependent unlike capacitor \$X_{c} = \frac1{2pifC}\$ and inductor \$X_{L} = 2pifL\$. Following Ohm's law, \$V = IR\$, the voltage of the resistor will not change since \$X_{R} = R\$, in contrast with capacitor and inductor whose voltages will change over frequencies.

But if your circuit is RLC, RL, or RC, the total voltage should change in varying frequencies.

  • 1
    \$\begingroup\$ I can now see the circuit in your question. I therefore stand by my answer. Since resistors are not frequency dependent, even though you vary the frequency of your AC source, voltage reading at any two points in the circuit will not change due to frequency. \$\endgroup\$
    – ellekaie
    Mar 4, 2014 at 2:36

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