An hour of lab is worth a week of talk

Thread Starter


Joined Nov 4, 2008
Mohotmoz' recent excellent question about resonance and Q is a subject near and dear to me. Here's how I handle the subject in my electronics classes.

Before I even broach the mathematics involved in resonance, I have my students BUILD a resonant circuit.


1) 1 mH inductor (I make my students wind their own with a powdered iron toroid core. I let them figure out on their own how many turns it takes to do this! Pure trial and error and an inductance meter. It's a great exercise for learning the FEEL for different real-world electrical values. Students will generally discover the "N squared law" on their own!).

2) .001 uF ceramic capacitor

3) 10k resistor

4) Signal generator or function generator (resonant F about 200KHz)

5) Dual trace oscilloscope

6) Lots of alligator clip leads

Wire the inductor and the capacitor in parallel. Connect "bottom" of tank circuit to ground terminal of signal generator. Connect signal generator output to "top" of tank circuit through the 10K resistor.

Connect channel A probe of oscilloscope to signal generator output. Connect Channel B probe of oscilloscope to top end of tank circuit.

Set generator to 10 volt output. Sweep generator between minimum and maximum frequency. Report what you see on the oscilloscope.

Class discussion.