0
$\begingroup$

I took a resonance curve (see below) for different (series) oscillating curcuits plotting I:f and found that the amplitude differs for different values of C and L. Why exactly is that?

enter image description here

Blue specs: $L=4.5mH,\ C=4.7\mu F$

Green specs: $L=4.5mH,\ C=1\mu F$

Purple specs: $L=18mH,\ C=1\mu F$

Picture of my measuring:

enter image description here

Improve this question
$\endgroup$
11
  • $\begingroup$ Think that you may need to provide more information on the resonant circuit and the graph. Was it a parallel or series resonant circuit? What kind of ac voltage or current source was used to drive it? What was the value of the resistance in the circuit? What is being plotted on the vertical scale of this graph? $\endgroup$
    – user93237
    Commented Jun 8, 2017 at 17:12
  • $\begingroup$ It was a series resonant circuit and there was no resistance involved (apart from the inner resistance of the coil). I plotted the current vs. the frequency as seen in the plot above, since it's a series curcuit. As for the voltage used to drive it: I don't have that information precisely but it probably was in between 0-7V. I added a picture of my measuring installation if that helps. $\endgroup$
    – user424862
    Commented Jun 8, 2017 at 17:22
  • $\begingroup$ But if you compare blue and green the inductor resistance stayed the same and only the capacity changed. $\endgroup$
    – user424862
    Commented Jun 8, 2017 at 17:30
  • $\begingroup$ Well, even small resistances have a big effect on the appearance of resonance curves because if there was really zero resistance then the peaks of these resonance curves would shoot up to infinity at resonance. What I don't understand offhand is why blue and purple curves have such different amplitudes even though they have very similar frequencies. The current peaks of these two curves correspond to the ac source driving nominally zero resistance loads (since the circuits are both at their respective resonant frequencies), so it seems that the amplitudes should be about the same. $\endgroup$
    – user93237
    Commented Jun 8, 2017 at 17:30
  • $\begingroup$ Oh, hold on. I think I know why the amplitude of the purple curve is so much smaller than that of the blue curve. The purple curve used an inductor of 18 mH while that of the blue curve used an inductor of 4.5 mH. Since the 18 mH inductor was probably made by simply wrapping more wire than the 4.5 mH inductor, the 18 mH inductor should have a higher resistance then the 4.5 mH inductor - by about a factor of 4 if the coil constructions are similar. That factor of 4 is consistent with the amplitude difference between the purple and blue curves. $\endgroup$
    – user93237
    Commented Jun 8, 2017 at 17:37

0

Reset to default