# Q & A: storing static electricity

Q:
I have induced static charges from a chair.My question is that whether it possible to store static charges ? If yes, what are the ways to do so?
- K.SRINATH (age 19)
A:
Sure! Just leave the chair sitting there. The static charges will stay there for some time (and on you, until you discharge yourself). How long it takes for the charges to relax back depends on lots of things, like the humidity of the air (which affects how well charges can migrate from one object to another).

Some materials can trap electrons and keep them from moving very effectively. Plastics can sometimes hold charges inside them for years. Of course it's not very useful if you cannot access them in some way, and trapped charge inside an object is typically screened out by charges which feel the electric field and collect on the outside to cancel it out.

You can store energy in a capacitor for later use (although "later" sometimes means microseconds later in the electronics biz). Just charge up the capacitor and you can discharge it when you close a circuit including its leads.

Tom

(published on 10/22/2007)

## Follow-Up #1: measuring static electricity

Q:
how do we measure static electricity? what is the unit for measuring static electricity?
- gurudas pai (age 70)
panaji, goa, india
A:
One simple measure is by the amount of charge separation. If one electrically connects the positive and negative regions current will flow between them. The total amount of charge that flows (the integral of current times time) is the amount that was separated to begin with. Typical units would be Coulombs or sometimes esu.
For other purposes, a more important measure may be the voltage between the regions, typically measured in volts or statvolts. This depends not only on the charges but on how far apart they are separated, and other details of how they are arranged in space. For other purposes the electric field (often measured in volts/meter or in statvolts/centimeter) is most important. It also depends on the spatial arrangement of the charges, but in a different way than the voltage does.

Mike W.

n.b.  There is an excellent article in Wikipedia on the subject.
http://en.wikipedia.org/wiki/Coulomb's_law

Lee H

(published on 10/22/2007)