Silly question about capacitors

[dieter]

Hi. As an amateur experimenter I have a simple question:
When I take two electrolyt caps, fill one to eg. 16 vdc, shorten the other so its empty, then I connect them +- and -+, to eachother, I get 8 v in both.


Since the energy in a cap is farad*v*v (pls correct me if I'm wrong), this means 50% of the energy has vanished. Where has it gone?

[MarkE]

Hi. As an amateur experimenter I have a simple question:
When I take two electrolyt caps, fill one to eg. 16 vdc, shorten the other so its empty, then I connect them +- and -+, to eachother, I get 8 v in both.


Since the energy in a cap is farad*v*v (pls correct me if I'm wrong), this means 50% of the energy has vanished. Where has it gone?

Almost of it goes into heat, the rest which is quite small goes into radiation.  Model each capacitor with a small series resistance, ESR.   All capacitors exhibit some ESR, and then of course the wiring has some resistance.  Most of the lost energy heats the wiring and ESR resistance.

[vasik041]

Almost of it goes into heat, the rest which is quite small goes into radiation.

I agree.

Here an illustration of the process.

[Cadman]

@dieter
Since you asked, the formula for caps energy is joules = 0.5 * voltage^2 * C

[Farmhand]

I think there is some element of impedance matching involved, for instance if we use a very low resistance inductor in the positive line and no switch in the current loop between the capacitors as shown in my drawing, as well as we are doing it for a reason so there is a load involved as well. Then the efficiency of the transfer can be better I think.

So the idea is the system is charged to 10 volts to begin with, the inductior is considered ideal and we switch the RL load in for 1.5 mS only once then calculate the power dissipated by the resistor as legitimate load power and calculate or measure the voltage on the two capacitors and calculate the energy missing.
Anyone want to put that in a simulator ?

Poynt99 did a good paper on this kind of thing. But I cannot find it. 

..