# Calculating inductance of an LR and RLC Circuit?

1. Apr 14, 2015

### WK95

1. The problem statement, all variables and given/known data
For both the LR and RLC circuit, a function generator is used to create a 1000 Hz square wwave of maximum amplitude.
1) For the following LR circuit, the resistance is set to a 100 Ohms. Determine the inductance, L. How does the inductance vary if the resistance were increased to 200 Ohms

2) For the following RLC circuit, the capacitance is set to a 0.001 micro F. Determine the inductance, L.

2. Relevant equations
2) F_0 = 1/ (2*pi* sqrt(LC))
ω^2 = (1/LC)(1 - (C*R^2)/(4L))
ω=2*pi*f

3. The attempt at a solution

1) I can't find any formulas for this one.
2) For question 2, I don't know which equation should be used. Also, I assume that f=1000Hz. For the second equation, R is the total circuit resistance, C is the capacitance, and L is the inductance.

Last edited: Apr 15, 2015
2. Apr 15, 2015

### WK95

I've found an equation for question 1.

V=V_0(e^(-Rt/L))

3. Apr 15, 2015

### WK95

For question 1, I got the inductance to be 0.114 mH.

4. Apr 18, 2015

### WK95

bump

5. Apr 19, 2015

### rude man

You did? Without knowing anything about the signal at "Ch. 1"? Wow! Show us how!

6. Apr 19, 2015

### SammyS

Staff Emeritus
Please give the problem statement as it was given to you. It clear that some critical information is missing.

What does it mean for the function generator to produce a wave of maximum amplitude?

Is it perhaps the wave at Ch. 1 which has to have maximum amplitude?

7. Apr 19, 2015

### WK95

Yes, my apologies. I've neglected to include the relevant oscilloscope readout.

Vertical Scale: 100mV/DIV
Horizontal Scale: 50 microsecond/DIV

Here is a the function generator used. Notice the AMPL knob to the right. Maximum amplitude means turning it all the way counterclockwise.

8. Apr 19, 2015

### WK95

Simple. Since I didn't know anything about what was in Ch. 1, I simply had to find it out. You can as well if you were to make the circuit as shown in the initial post.

9. Apr 19, 2015

### rude man

Yeh, but you didn't know L either. You were supposed to find L given Ch. 1.
I see you did post the Ch 1 waveform later. Much better.
It would further be helpful if you provided us with the amplitude of the square-wave generator, although one can estimate L based on the decay profile in Ch. 1.