What do capacitors do?

[Tasmaniak]

Thats why I use the test light...or a 10watt 10ohm resistor...couldn't find either once so I used a 1watt resistor....bloody hell it got hot!

 

[Cameron]

you guys are way too smart!!!!

 

[Tasmaniak]

Sometimes....we outsmart ourselves!

 

[garfa]

with the light and the cap trick i gather thats because of the photons being emitted, they are transfering their energy (about 1-2eV per photon) to the car terminals. it would make sence. it sounds like it is (sorta) the reverse of the photoelectric effect. eg: instead of releasing voltage from a piece of metal using a light (i think it needs to be uv? or around that wavelength) using light to charge it.
i hope thats clear. doesnt seem to me but then again its pretty early (10am!)

 

[dephilile]

Huh, I thought you would use the light to tell you when it’s charged because when a capacitor is fully charged it can be thought of as an open circuit. No charge flows meaning the light wouldn’t light up. I don’t think it has anything to do with photons being emitted.

Plus, I’m not really 100% sure about this but I would have thought that the theory of electrons getting pushed up into a higher orbit about the nucleus and then dropping back and releasing a photon was only applicable for fluros and neons. I’m not sure about a normal light bulb. I thought it just glowed really bright because of it’s resistance. Maybe the same thing is happening, just within the wire. I dunno. Photons are getting created somehow.

 

[Phreddy]

Hey Deph. :thumbsup:

I think the scheme here wasn't to hook up the lamp in series with the cap (although of course, that's what King and I were referring to) but I think what Spac was talking about was just sitting the cap in front of the lamp - no electrical connection as such. What you say is absolutely correct - if you DO hook up a globe in series with the cap, once the lamp goes out the cap is charged, given that a charged cap is open circuit to DC. (well, for all practical purposes anyway)

I can see what Garfa is on about - I think - but jeez, I still reckon it's a rather wasteful way to charge a cap in comparison to simply hooking it up with a resistance in series - such as a test light, resistor, or whatever. Great practical demonstration, but your battery will get a bit upset....

Still - it's a neat trick!

Cheerz.

 

[dephilile]

Well, can someone please explain to me why you would put a light in parallel with the cap? What does that do? Why not just throw it straight on the battery and try to guess when it’s charged?

 

[dephilile]

Oh, hold on. So all your doing is shining a light at the capacitor to charge it? I would have never thought that would work. WTF!

 

[garfa]

yeah when the light bulb filament ihas current passed thought it it heats up then starts to glow. remember that infrared is just before visable light so yeah photons are being emmitted. i probably read your post wrong.
i can see how in theory if you were shining a realllllllllly bright light (light meaning something that emitts em radiation of sufficent energy) on the caps terminals that it might charge. this would need to be done at the syncrotron or some where with high enought energy "light". remember that a cap discharges (thanks ray) and hence it will probably discharge faster than its being charged if a light bulb is used.

 

[Morgasshk]

Ok, now I feel dumb...

I was thinking a Capacitor is an extra power storage vessel (and I guess it is of a type) and that if you want to play stereo with power off for extended lengths of time, the power from the Capacitor will be used rather than drain the battery dead?

Correct me if I'm wrong? (nicely please!)