Calculating inductance of an LR and RLC Circuit?

• WK95
In summary, for both the LR and RLC circuit, a 1000 Hz square wave of maximum amplitude is produced using a function generator. In the LR circuit with a resistance of 100 Ohms, the inductance, L, is found to be 0.114 mH using the equation V=V_0(e^(-Rt/L)). If the resistance is increased to 200 Ohms, the inductance will vary. In the RLC circuit with a capacitance of 0.001 micro F, the inductance, L, can be determined using the equations F_0 = 1/ (2*pi* sqrt(LC)), ω^2 = (1/LC)(1 - (
WK95

Homework Statement

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[/B]

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

Homework 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:
I've found an equation for question 1.

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

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

bump

WK95 said:
For question 1, I got the inductance to be 0.114 mH.
You did? Without knowing anything about the signal at "Ch. 1"? Wow! Show us how!

WK95 said:

Homework Statement

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[/B]

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

Homework 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.
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?

SammyS said:
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?
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.

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

WK95 said:
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.
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.

1. What is inductance?

Inductance is the ability of a circuit to store energy in the form of a magnetic field when an electric current flows through it. It is measured in units of Henrys (H).

2. How do you calculate the inductance of an LR circuit?

The inductance of an LR circuit can be calculated using the formula L = L = R * τ, where L is the inductance, R is the resistance, and τ (tau) is the time constant. The time constant is found by dividing the inductance by the resistance (τ = L/R).

3. What is the formula for calculating the inductance of an RLC circuit?

The formula for calculating the inductance of an RLC circuit is L = √(1/((1/C) - (1/(C + R)))) where L is the inductance, C is the capacitance, and R is the resistance.

4. How does the number of turns in a coil affect inductance?

The number of turns in a coil directly affects inductance. The more turns there are, the higher the inductance will be. This is because each turn adds to the magnetic field and thus increases the amount of energy that can be stored.

5. Can inductance be negative?

No, inductance cannot be negative. It is a physical property of a circuit and must always be a positive value. However, it can have a negative effect on the behavior of a circuit, such as creating a negative phase shift in an AC circuit.

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