1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Charging an edlc with 1 lead

  1. Jan 27, 2016 #1
    Why can't I charge my supercapacitor with 1 wire? If the ions in the electrolyte make up the opposite electroldes, why won't it store charge when I charge it with 1 wire? It makes since for it to hold less charge but it's not charging at all.

    I'm using a grounded battery. 1 wire to my supercap and 1 to ground.
  2. jcsd
  3. Jan 27, 2016 #2
    You need to connect both terminals of the cap to the anode and cathode of the battery to charge it. The voltage at a point has to be in respect to something. I think that if you hook up your battery to earth ground and the capacitor to earth ground, and then run a wire between the positive terminals, it will charge.
  4. Jan 27, 2016 #3
    Thanks for the help. I don't understand why both are needed. If you connect a conductor to a voltage source, it becomes charged to the voltage. Why then won't the conductor attract ions to it's surface?
  5. Jan 27, 2016 #4
    What about this situation? Should these supercaps charge? I don't have a second supercap of equal parameters; otherwise, I would try it out. edlc.png
  6. Jan 27, 2016 #5
    Something can only have voltage with respect to something else. Hooking up a single wire is meaningless, unless you are defining that wire as ground or "0" volts. When we say, for instance, 9 volts, we mean 9 volts potential with respect to our choice of ground. A single wire can't charge something without a complete circuit due to this.

    Scroll down and look at the battery picture and explanation, it might help you understand even though it isn't exactly what you are asking.

    Edit: Yes, those caps would charge, I think. I connected it on Icircuit and it seemed to think so, though not really charged in a useful way. Your "ground" basically makes a short between both ends of the capacitors. If you just wanted to charge the cap, hook them both in parallel to the positive terminal, then the other end to ground, and the negative terminal of the battery to ground. That will charge them as long as the ground used is the same... Which means you're back to using a closed circuit in practice.
    Last edited: Jan 27, 2016
  7. Jan 27, 2016 #6
  8. Jan 27, 2016 #7
    Anything conductive can be used as a ground reference. "Ground" just means the place you define to be 0 volt potential. It does not mean actual earth, or somewhere current dissapears to, it's just convention.
  9. Jan 27, 2016 #8
    Thank you very much karmaslap.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook