WEBVTT

00:00.000 --> 00:07.611
The GBF, a low frequency generator, supplies a coil in series with a resistor

00:07.611 --> 00:16.288
Circuit RL series: resistance R (intensity image in blue), inductor (coil in blue)

00:16.288 --> 00:27.429
Mass at the common point of the series connection: coil and resistor

00:27.429 --> 00:39.917
The oscilloscope uses an inverting probe to compensate for wiring reversal

00:39.917 --> 00:49.556
At 50 Hz, the red coil has much lower impedance (and therefore amplitude)!

00:49.556 --> 00:56.324
I increase the frequency of GBF

00:56.324 --> 01:07.439
The red amplitude increases because Z of the coil (Z # L * 2 * pi * f), neglect R

01:07.439 --> 01:15.554
The amplitudes are now identical

01:15.554 --> 01:25.232
The value of the inductance is checked by neglecting R (not significant at 2 kHz)

01:25.232 --> 01:35.801
Z = Root (R² + X²); R² negligible in front of X (X = L * 2 * pi * f)

01:35.801 --> 01:44.347
2 * pi * f = pulsation

01:44.347 --> 02:04.997
Omega = 12,560 (pulsation: 2 * pi * f)

02:04.997 --> 02:16.750
Impedance coil = impedance (and therefore resistance because pure resistor) = 250 Ohm

02:16.750 --> 02:29.906
0.0199 Henzy: 20 milliHenry: 20 mH

02:29.906 --> 02:48.517
Check with inductor-meter

02:48.517 --> 02:58.927
19.7 mH for 20 mH read and calculated :-) We are good!

02:58.927 --> 03:17.170
Its continuous resistance is 26 Ohm, we will check if this changes our calculations ...

03:17.170 --> 03:31.242
By applying X = Root (Z² - L²), we find 248.6 Ohm instead of 250 (...)

03:31.242 --> 03:37.622
0.5% error, therefore negligible, the measurement on the oscilloscope being less precise