Can you store electricity?

[Swivelguy2]

The energy does not exist in the plates, it exist in a field between the plates caused by the imbalance of charge. Remove either plate and the energy is gone. What you would have is a piece of metal with more or less electrons but no energy. For an experiment , power a capacitor and then carefully take it apart so it is two different plates. Now put it back together. Measure the voltage. The energy you put into it will be gone.

I'm pretty sure you're dead wrong, but this is a bit unclear. I think you mean this:

1. Connect a voltage source to either side of a capacitor, charging it up
2. Disconnect the voltage source, leaving the capacitor charged
3. Separate the plates
4. Bring the plates back together
5. Measure the stored charge separation

In this case, the charge on each plate is preserved when they are separated. They're insulated from each other and hopefully from everything else, so the charge can't go anywhere! Because the plates are attracting eachother (due to their opposite charges), you actually have to put energy into the capacitor (by pulling hard) in order to separate the plates. The farther apart you get the plates, the more energy there is in the capacitor!

The energy stored in a parallel plate capacitor is: U = 1/2 * C * V^2 = 1/2 * Q^2 / C, where C is the capacitance, Q is the stored charge separation, and V is the voltage between the plates.

In the example I outlined above, Q stays constant as the plates are separated and C decreases, so the energy increases as you pull the plates apart. When you bring the plates back together, you'll have to pull to resist their motion as they attempt to slam into one another. The capacitor will be losing energy, dissipating it into your arms as your bring the plates gently closer together.

In any case, after separating the plates and bringing them back to where they started, you will most certainly have the same amount of stored charge separation, stored energy, and voltage difference as you did before you separated the plates - unless you've let some charge leak out somehow (which we all know is inevitable in the real world).

What capacitor did you use to try this?

You can use something like this: big picture. I don't know what they're doing with the ring in the middle of the picture, I'm just talking about the adjustable capacitor at the left side. In fact, I did this very experiment several years ago in high school.

 

[TecHNooB]

Conversations about energy always baffle me. ^ This did not help.

Hm.. it all works out on paper. Now I need to figure out why I thought big C = more energy.

 

[William Gaatjes]

In this case, the charge on each plate is preserved when they are separated. They're insulated from each other and hopefully from everything else, so the charge can't go anywhere! Because the plates are attracting eachother (due to their opposite charges), you actually have to put energy into the capacitor (by pulling hard) in order to separate the plates. The farther apart you get the plates, the more energy there is in the capacitor!

The energy stored in a parallel plate capacitor is: U = 1/2 * C * V^2 = 1/2 * Q^2 / C, where C is the capacitance, Q is the stored charge separation, and V is the voltage between the plates.

In the example I outlined above, Q stays constant as the plates are separated and C decreases, so the energy increases as you pull the plates apart. When you bring the plates back together, you'll have to pull to resist their motion as they attempt to slam into one another. The capacitor will be losing energy, dissipating it into your arms as your bring the plates gently closer together.

In any case, after separating the plates and bringing them back to where they started, you will most certainly have the same amount of stored charge separation, stored energy, and voltage difference as you did before you separated the plates - unless you've let some charge leak out somehow (which we all know is inevitable in the real world).



You can use something like this: big picture. I don't know what they're doing with the ring in the middle of the picture, I'm just talking about the adjustable capacitor at the left side. In fact, I did this very experiment several years ago in high school.

I have slept very bad for the last 3 days, so i might as well be totally wrong.

Is the idea in your thought experiment not that you use mechanical energy to separate those plates. Because with what i understand from it, you are converting mechanical energy into electrical energy by moving two opposite charged surfaces away from each other. That sure does sound like the cat and the comb or carpet and the comb. But that i can understand. But i have difficulty to accept that the increase in distance in your example also means that the amount of electrical energy increases.

But the point is that you must first create that electric flux field with the power source and after that you can use mechanical energy to increase that field, or am i wrong ?

 

[KCfromNC]

He basically said something like this:

"Bananas are yellow."

You said:

"No, bananas are fruit."

Not to mention the bigger problem that electric current is most definitely not defined to be the movement of electrons. Us EE types tend to forget that there's a lot of electricity going on in chemical and biological systems in addition to the stuff happening in wires and semiconductors.

 

[TecHNooB]

Not to mention the bigger problem that electric current is most definitely not defined to be the movement of electrons. We EE types tend to forget that there's a lot of electricity going on in chemical and biological systems in addition to the stuff happening in wires and semiconductors.

Based on this thread, I don't think you're allowed to use the word electricity in any statement you make. Elaborate on the bolded part plz.