Variable capacitor understanding ?

[vicegrip]

I couldn't stay interested way back in electricity class.
Oscilator circuits what ?

I just got so intrigued str8'ning out the fins that the other
dextrously challenged kids mangled.

And being a boy-metalica I mastered soldering "at sight-at touch".
So ended my undestanding of oscillator circuits.
http://www.mtmscientific.com/cap3.jpg

Now starting at the high freak generators in my tig-welders,
is the "overlap" of these fins, a sort-of variable-spring???
designed to constrain / capture a reaction at a frequency that
is a result of how much overlap the two sets of fins is set at.????

So that a 12-year-old's simple bread-board radio experiment
can only recieve 92 WOKY , or so that my Linde only generates
70k's or so of High frequency.

An over-worked mechanical mind, needs to know.
Thanks .........
vg

[usmcpop]

A bit here: http://en.wikipedia.org/wiki/Variable_capacitor

It's just another form of capacitor - metal plates with air as the insulator instead of mylar or some other substance. The fact that the plates can be shaped a certain way and the overlap adjusted makes them very useful for tuning. I used to have an old Hewlett-Packard oscillator that had a variable air-cap capacitor about the size of a large soup can.

More here: http://electronics.howstuffworks.com/capacitor.htm