Re: Capacitor energy experiment

[John Mallinckrodt <ajm@CSUPOMONA.EDU>]

Question 1

> Suppose I have two 1 F capacitors, each with potential difference 1
> V.  What physical difference between the capacitors makes one of
> them "store" 1 J while the other "stores" 0.5 J?

Suggested answer 1:

> A stronger electric field due to closer plate spacing or a good
> dielectric insulator would do it. A larger plate surface would too.

No, it wouldn't. The energy stored by a 1 F capacitor charged to 1 V is 0.5 J.

Question 2

> Do I understand that two identical capacitors are supposed to have
> the same potential difference across them while having different
> charges? Since the charge on the plates is the source of the
> electric field between them, how is this possible?

It isn't.

--
   A. John Mallinckrodt        http://www.csupomona.edu/~ajm
   Professor of Physics      mailto:ajm@csupomona.edu
   Physics Department         voice:909-869-4054
   Cal Poly Pomona              fax:909-869-5090
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