Elastance
The unit of elastance is the volt
per coulomb or, unofficially, the daraf (D). So if a
capacitor has capacitance C = 1 nF, it has elastance S =
1 GD.
The elastance of a capacitor, its charge, and the voltage across it
are therefore related as follows:
and
Because capacitances add reciprocally in series and add directly in
parallel, elastances add directly in series and add reciprocally in
parallel:
| Capacitance | Elastance |
Series |
1/C = 1/C1 + 1/C2
|
S = S1 + S2
|
Parallel |
C = C1 + C2
|
1/S = 1/S1 + 1/S2
|
Elastance has the same series/parallel behavior as resistance and
inductance.
All of this probably doesn't seem very useful. It isn't. No one ever
uses elastance. We will only refer to elastance in one or two pages
in this set of lessons, and then only because elastance has the useful
property that the voltage across a capacitor is equal to its charge
multiplied by its elastance.
I swear I am not making this up. See the American Institute of
Physics Handbook, page 5-6.
Copyright
2000
Rensselaer Polytechnic Institute. All Rights Reserved.