Electric OU: Supplement: CAPACITORS….How do THEY work ??
The mysterious capacitor reveals some of its secrets. Here I take a 10000 picoFarad poly capacitor through some paces. I took one and sectioned it on the bandsaw to show its internal structure. (Believe it or not, that sectioned cap still works !! Although it’s quite leaky now, and I wouldn’t take it to 500 V.) Then using an intact capacitor of the same make and model and paint job, I show that it will not pass DC at 12 volts to light a small automotive light bulb. But what about AC? I use the Interstate F43 Function Generator to light up the bulb, without the capacitor, with a 12 volt peak AC signal at the American line frequency, 60 Hz. Then I show that the capacitor blocks even this AC frequency totally. But what about RF AC, radio frequencies in the hundreds or thousands of kiloHertz? Let’s check. The Ainslie circuit referred to in the video uses 5 each IRFPG50 mosfets, with 4 of them in parallel. The Ciss input capacitance of this mosfet is given as 2800 picoFarads, thus 4 in parallel will have a capacitance of 11200 picoFarads, quite close to the value of the capacitor used in this demonstration. The mosfets in the Ainslie circuit are perfectly capable of passing AC current at the oscillation frequency of around 1.5 MHz…. almost as easily as a simple short piece of copper wire, whether or not they are in the “ON” state. And yes, Virginia…. a function generator can both PASS and SOURCE current.
