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Re: Solenoid



Hi,

I would suggest measuring L in an LR circuit driven by a
sine wave. Measure the current, I, in the circuit by way of the
voltage drop across the resistor, V_R, and the voltage V_L across the
inductor. The Inductive Impedance X_L is then:

X_L = V_L / I.

If the angular frequency is w then the inductance L is:

L = X_L / w

If the resistance is R, one can put all of this together to get:

L = ( V_L R) / (V_R w )

or convert this into something to plot with L as the slope.

One can use the peak values of V_L and V_R.

Thanks
roger Haar
U of AZ



*****************************************************

On Tue, 26 Nov 1996 msantos@etse.urv.es wrote:


Any one else tried to measure L? What do you recommend.

My instinct would be to measure the resonant frequency of a series
R-L-C circuit which included the unknown inductance. Fairly high quality
capacitors are usually available over a wide range of capacitance.
With a little additional effort you can also get a pretty good value
for Q, as well.


--Jim(pengra@whitman.edu)


Well, there probably are, but my (little) experience is that the
usual ones you get have a 20-25% tolerance.An MKT 2.2 microF costs
around 3-4$. My believe is that price will increase quicker than
% tolerance. Indeed I do want them for a lab session where I need
10 + (10;every student breaks his capacitor) + ...same old story.

Any way, I will consider to have them measure L in a earlier
lab session with such a resonant circuit.

Thanks
Regars
MA Santos
msantos@etse.urv.es