Science Buddies: "Ask an Expert"

Hello. I'm doing a Thomson Coil for my science project. I have read that if I put a capacitor in series in the ciruit (120V, 60 Hz) for the solenoid that with careful tuning to 60 hz, an aluminum ring over the soenoid, instead of jumping, will oscillate up and down. What values for or type (variable/trimmer?) of capacitor do I need? My coil is done and works. Now I would like to add the capacitor. I have also read that a resistor may be needed. If so, what type and values?

Here is the link to the plans we used to build the coil: http://kossover.squarespace.com/journal ... -coil.html

Looks very straight forward. I saw no mention of a capactor in the plans, what are you referring to?

What you are referring to is observing the effects of an RC (Resistor-Capacitor) circuit. The capacitor causes the voltage to the inductor, your Thompson coil, to gradually increase and decrease. This changes the magnetic field and the eddy currents, which affect the way the rings move.

I suggest you go here to begin learning about RC circuits. http://en.wikipedia.org/wiki/RC_network

You can broaden your learning from this starting point and be able to figure out what values of resistors and capacitors will do the job you want. Be sure to consider how much current you will be putting through these devices when you select your components.

Good luck and have fun!