Capacitors store electrical energy by way of capacitance and is measured in farads - The Farad is the amount of charge capacity that a capacitor can hold. Another way I understood it was that it’s the amount of current that it takes to increase voltage within the capacitor by 1volt/second. IE how much current has to pass into the capacitor before the rate of voltage increase = 1 volt/second.
Capacitor Part 1:
@whixr mentioned to me that capacitors are often used to allow AC current but not DC current, and so are known as DC blockers. So another metaphor that he’s come up with is the following. Capacitance is like a rubber membrane in a barrel (brown line). Pipes are attached to each end of the barrel and a pump connects those pipes. You can only pump water in one direction so much, then the rubber wall will not stretch anymore (stretching possible according to dotted black lines). Picture:
With DC current, that’s like pumping water from only the left to the right side (for instance). The water can only go against the rubber membrane so much, before it stops. If however, you have AC current, it’s like the pump pumping water from the left, then the pump pumping water from the right. And the water ends up going back and forth. So that anything in between the pump (power source) and barrel (capacitor) can take advantage of that current. So too capacitors do not allow DC current through and only allow AC current to work upon it.
Capacitor Part 2:
This is of my own making from studying capacitors and from what Whisker’s told me about capacitors. Essentially a capacitor’s like a cul-de-sac, and kids running into the cul-de-sac is like electrons going into one side of the barrel or electrode. They can’t go past the cul-de-sac (re: DC current). The only way is to go back the way they came in (re: AC current).
Capacitor Part 3:
So we have a sandwich: two conducting surfaces called electrodes and between these two electrodes, an insulating dielectric (wood/rubber/air). Remember, conductors allow current to flow easily and insulators do not.
This is when no power is running through yet - when both electrodes have the same number of electrons as the other, and therefore no voltage/electric potential has been induced. (Our dielectric is Gandalf)
And I’ve gone and gotten the battery on and as always, the current will go towards the positive electrode. Current will go in the only direction it can towards the negative electrode of this capacitor.
Well now that you’ve gotten all of the electrons on one side of the equation, there’s this electric field that’s been created, and it’s got a huge amount of energy potential behind it. I’ve gone ahead and taken the battery away.
And when you end up putting both ends of the capacitor on the same conductor, you get a huge rush of electrons rushing back to balance things out = pow! bam! crackle!
Capacitor Part 4:
When a capacitor is connected to a circuit, as current flows into it, it develops an electrical potential (seen above) - this is known as voltage though measured in farads (amount of current to increase the voltage in the capacitor by 1volt/second). Remember that the capacitor always wants to “reequilibrate” or “leak” the current it’s been given back into the circuit. That’s why capacitors are known as voltage smoothers. Example:
Alright. So we’ve got a power source that’s not very reliable - sometimes it gives out a certain amount of power, and when the weather’s bad, it gives out another amount of power. All within a certain range, but not precise all of the time. Everything’s connected to ground. And we’re trying to light a light bulb. So when the power source is pushing forth too much power, it gets sucked up by the capacitor and the capacitor’s “rubber membrane” absorbs that extra energy. However, should the voltage falter from the power source, the capacitor then takes up the slack and releases its energy into the circuit. This allows “voltage smoothing” to occur, and the light bulb would never know the difference!
These are the more common types of capacitors as well as different specs for each. (http://i.cmpnet.com/planetanalog/2007/06/C0201-Table2.gif)
Next article - how to read capacitors!