Polarized capacitors in series

The value of capacitor in series follows a formula similar to resistors in parallel. In the above example two 10 microfarad capacitors in series is equivalent to one 5 microfarad capacitor.

When you connect several capacitors in series to a battery with voltage V, each of the capacitors acquires an identical charge Q. The charge on the plate connected to the positive terminal of the battery is +Q and the charge on the plate connected to the negative terminal is −Q. Charges are then induced on the other plates so that the sum of the charges on all plates and the sum of the charges on any pair of capacitor plates is zero. However, the potential drop V=Q/C on one capacitor can be different from the potential drop on another capacitor, because capacitors can generally have different capacitances. Generally, any number of series-connected capacitors is equivalent to a capacitor whose equivalent capacitance is less than the smallest of the capacitances in the series combination.

Good question. javagoza is right about ideal capacitors.

I assume the middle plates tend to drift to the voltage of whichever capacitor has the most leakage. Presumably if this causes the other capacitor's dielectric to start breaking down this would pull the voltage back more in the middle.

I suspect you're confusing the arbitrarily named anode (+) and cathode (-) with electric charge. Those designations are relative to the direction of the electric field and less about the type of charge associated with them.

First, recognize that everything has a capacitive element. So your visualization only works in non-existent ideal capacitors.
 
For that reason, the charge has to be distributed among the plates. And if we know the applied voltage and the capacitance values, we can determine the effective charge since it is related to the strength of the electric field.

Also, don't confuse "electrons" for the charge. Electrons are the carrier, not the charge. So electrons aren't accumulating anywhere. Charge, relative to the strength of the electric field, is.

Last, for this discussion, it does not matter if the capacitors are polarized! Polarized capacitors are a property of the dielectric and the direction it grows. The net charge is the same whether it is a non-polarized or polarized capacitor because it is relative to the electric field. The only difference between the two is what happens to the dielectric when that field is applied. For example, the dielectric starts to break down with a "negative" electric field, in a polarized capacitor.

javagoza said:

When you connect several capacitors in series to a battery with voltage V, each of the capacitors acquires an identical charge Q.

This is correct. And when in doubt, bring the multimeter out:

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RE: Polarized capacitors in series

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This is a lovely question most capacitors are already polarized like an anode or a cathode. Anode being positive and cathode being negative. You should not think of a capacitor as a battery because it seems like what you're describing would be something that would happen in a battery. 

Essentially they don't hold the charge on opposite plates in the "middle" 

Nrg is just moving back and forth.

youtube.com/watch

youtube.com/watch

Nice looking supply. Presumably if you left the meter connected, the voltage would drift as the meter impedance discharged the cap.

dougw said:

Nice looking supply.

Not high tech. But highly helpful:  Humble LAB equipment: METEX MS-9150 4-in-1 Test Setup