# 2 capacitors in series w/ a dielectric.

1. Oct 11, 2015

### Iron Charioteer

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Two capacitors (lets call them C1 and C2) in series are connected to a voltage source and charged. While still connected to the source one of them is filled with a dielectric (lets say C2 is filled). I know the charge on C2 will change by a factor of K because the source keeps the potential differences of each capacitor constant. But does the charge of the unfilled capacitor (C1) change?
This is more of a conceptual question.

EDIT: I got it. The charge on the unfilled capacitor remains the same.
I would delete the thread but i can't figure out how to do that.

Last edited: Oct 11, 2015
2. Oct 11, 2015

### Staff: Mentor

It doesn't, it keeps the sum of the potential differences constant.
It does not.
Changing the charge on one capacitor but not on the other would violate charge conservation.

3. Oct 11, 2015

### Iron Charioteer

Hmmm.... I guess i didn't know what i thought i knew. Haha!
So what you're saying is that the the charge on each capacitor remains the same but the potential difference of the capacitors changes; i.e.
Vtotal=V1+V2=q/C1+q/KC2.
So the rule for capacitors in series holds even when a dielectric is inserted into one of the capacitors?

4. Oct 11, 2015

### Staff: Mentor

I'm not saying that.
They apply before and afterwards separately, sure. They'll give different results, however.