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        R L C
This is a two week lab.

MOVIES

Please note: If the movie is too small,
please watch via youtube using the YOUTUBE button on bottom right of each video.
And, some videos have much higher quality. Find the HD version using the gear icon.

RLC: Part 1, Data Taking 




RLC: Part 2, Scope, RVS Output




DMM-01- Inputs and Selector for Amprobe 37XR-A Digital Multimeter



DMM-02- Measure Resistance with DMM Amprobe 37XR-A 



DMM-03- Measure Capacitance with DMM Amprobe 37XR-A



DMM-04- Measure Inductance with DMM Amprobe 37XR-A






Begin Q&A Forum for "R L C"

How do you convert henrys to farads?Anonymous
Tue. 04, Mar 2003, 18:55
Henry is a measure of inductance.
Farad is a measure of capacitance.
So, you don't normally convert from one to the other.
But, in the Impedance equation Z = √[(ωL - ω-1 C-1)2 - R2]
one can see that ωL and ω-1 C-1 must both have units of Ω
I hope this answers your question.
{Read this on the Q&A website so that the goofy code (ω) appears like symbols.}
Douglas
Wed. 05, Mar 2003, 08:20

In question #6 on the RLC prelab, we are given the resistance of a coil and a resistor. We do not know if the elements are in series or if there is a capacitor in the circuit. I tried N/A as the answer but this was wrong. Are we to assume that the elements are in series and this circuit does not contain a capacitor (Xc = 0) and apply the Z equation (this was the approach used in lecture)?Anonymous
Wed. 24, Mar 2004, 10:59
If we stated "What is the impedance of the circuit," the answer would depend on what frequency it was.
If we state what is the resistance of the circuit, it just means the resistance.
Yes, they are in series. That is what an RLC circuit is.
I think I will reword the question to say:
"What is the resistance of the circuit when driven at its resonant frequency?"
That way, anyone thinking of impedance instead of resistance will be automatically driven back to the base value for resistance. At resonant frequency, Z=R. But only at the resonant frequency.
Thanks for asking.
Douglas
Wed. 24, Mar 2004, 12:03

Douglas,
In trying to find the units of Z (question #2) I solved for units from the equation, and also looked it up in the book - I'm quite sure it's Ohms. However, I answered Ohms the first time I took the quiz, was marked wrong, then answered V/A (equivalent to Ohms) and was also marked wrong. Can you tell me what's going on here?
Anonymous
Sun. 28, Mar 2004, 10:21
If symbols don't appear right in your email application, then view on the web for best viewing.

Look again at the equation for Z.
Z =[ (ωL - (ωC)-1 )2 + R2 ] 1/2

It must share the same units as
XL, XC-1, and R.
XL --> [Henry/s]
XC-1 --> [s/Farad]
R --> [Ω]
And we know that Z = V/I, so it must also have units of [V/A], as you already knew.
I hope this helps, alot.

P.S. I just changed the Q&A email format to be html-ized. Can you read this email okay? I mean, do you see symbols and sub and superscripts? Or do you see a bunch of coding gibberish? Thanks for letting me know.
-Douglas



Douglas
Sun. 28, Mar 2004, 15:45

Douglas,
I am unsure about what lissajou figures are, I do not recall discussing them in class and can't find any information on them in the lab manual or in my text book. Could you please help.
Thankx
Vann, Cassie
Sun. 04, Apr 2004, 13:23
sasscass3@aol.com
The Lissajou figure (paramtric plot) is the O'Scope plot of
Voltageresistor vs. Voltagesource.
For RLC, the two frequencies are identical. But there is a phase difference between them at any f except resonance. When the two are in phase, they both hit a max at the same time and they both hit zero at the same time.
Douglas
Mon. 05, Apr 2004, 07:54

Douglas, I have some questions regarding the RLC pre-lab. After watching the movies, reading the manual, and reviewing your responsed to previous questions, I still do not understand how to convert henrys to farads. Also, I have no idea what to do with #6. I'm not sure which equation to use to calculate this value. Thanks for your help.Anonymous
Wed. 06, Jul 2005, 16:00
J,
At resonant the frequency the only impedance is due to resistors because the impedance of the coil and capacitor cancel. But the coil is made of a long length of wire, therefore it has resistance just like a resistor does. So, at resonance, the resistance of the circuit is equal to the sum of the resistor and the resistance of the length of wire in the coil.
I don't know where in the quiz it asks you to convert a Henry to a Farad. These units are not synonomous. But be careful, because a Farad might be related somehow to Henry-1... Hmmmm....
https://physics.nist.gov/cuu/Units/units.html
Also think in terms of the Z equation. What are you adding? Do units have to match in order to add?
Douglas
Thu. 07, Jul 2005, 13:20

Hi Douglas, I am having trouble with the prelab question 6. I am not sure how to tell what is staying the same. My initial thought was that angular frequency was staying the same, but I got that wrong. Will you please help me here?Anonymous
Wed. 17, Oct 2007, 21:30
What stays the same?
Impedance, Current, XL, XC, Linear Frequency, Angular Frequency,
All of These, None of These

Frequecny (f) [Hz = cycles/second] is changing throughout experiment.

Angular Frequency (ω) = 2πf [rad s-1]

XL = ω L = 2πf L

XC = ω-1 C-1 = (2πf C)-1

Impedance (Z) = √ [ (2πf L - (2πf C)-1 )2 + R2 ]

Current (I) = V Z-1

Are any of these not frequency dependent? Or are they all dependent on the driving frequency of the circuit?
I hope this helps a little. :)
Douglas
Thu. 18, Oct 2007, 08:39

Hey Doug,
For the question no.6 I realized that at resonance, XC = XL, and so Z becomes R. But yet when I wrote my answer as 9.90 Ohms it marked me wrong. This got me confused as to whether I understood the concepts well enough or not?
Hope you'll be able to help me out.
Thanks a ton.
Sequeira, Emmanuel
Wed. 30, Mar 2011, 23:01
esequei2@msudenver.edu
You are correct that Z = R at resonance because XC = XL at resonance. But the basic resistance in the circuit is made from two things: a) resistor and b) coil.
In fact, many RLC circuits have no "dedicated resistor" since the coil (being a long length of wire) has resistance. So the coil serves two purposes in the RLC circuit. 1) Resistance and 2) Inductive Reactance.
Douglas
Thu. 31, Mar 2011, 05:02

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