# Series Resonance Help

Discussion in 'Homework Help' started by trav, Dec 8, 2011.

1. ### trav Thread Starter New Member

Dec 8, 2011
7
0
Connect the 50 Ω output from the function generator to the oscilloscope input and establish a sine wave on the oscilloscope with the following characteristics:
a. f = 100 Hz, Vmax = 500 mV
Disconnect the output of the function generator from the oscilloscope and apply it to your circuit.

Giving me the result:

f(hz) Vr(V) vc(V) vl(V)
100 0.96 0.65 0.06
150 0.13 0.63 0.08

It then asks me to use these results to calculate the following parametersfor 100 and 150hz:

I (A)
XL (Ω)
XC (Ω)
Z (Ω)

How do i do this?

Last edited: Dec 8, 2011
2. ### who_me_yes_you New Member

Dec 7, 2011
8
0
Ohms law my friend...and depending on whether you know the values of capacitance, inductance and resistance and have a basic knowledge of complex numers this is how it is calculated

Vr + Vc + Vl = total voltage (Vt)

Xl = jwl=2*pi*f*l
Xc=jwc=2*pi*f*c
Z=R+(jwl-jwc)

It = Vt/Z

3. ### crutschow Expert

Mar 14, 2008
13,472
3,359
You only need ohms law to calculate the various impedances. Since you know that the currents are the same in all devices for a series circuit, it's a simple matter to calculate each impedance knowing the current through, and the voltage across, each impedance.

4. ### trav Thread Starter New Member

Dec 8, 2011
7
0
Would i be right in saying:

1. I v/r 0.0957/100

2. Xl = 2pi x f x l

3. Xc = 1/2pi x f x c

4. Z = √rsquared+(Xc-Xl)squared

5. tan-1(Xc-Xl)/R

I think im right here but would like some clarification especially with the first one of all things lol

Dec 26, 2010
2,147
300
In your first post, you had Vr(V)=0.96. Now it seems to be 0.0957. Which is it to be?

6. ### trav Thread Starter New Member

Dec 8, 2011
7
0
0.096 sorry my mistake but thats not really my issue here. More intrested in the formulas being correct.

Last edited: Dec 8, 2011
7. ### trav Thread Starter New Member

Dec 8, 2011
7
0
Forgot to mention a 100ohm resistor was used and thats were im taking my 100 figure from in Q1

8. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
After you get it sorted out in your head figure out the voltage the components are dropping. I love to give this question to beginners, because the results are so surprising.

9. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
Interestingly, the experimental procedure seemed to make no directive to the student to adjust the generator frequency in order to find the series resonance condition.

Is the OP aware of the measurement indication(s) of when resonance has actually occurred?