Connect thin wire to +, wide are electrode (say piece of Al-foil) to -,
apply 30kV between them (doing it all with corresponding care) - and,
to your surpize, you will see that both electrodes move.
Not just jump - move continuously, in direction from
wide to thin electrode!
Here is one of devices employing this idea, made by J. Naudin:

Having completed school physics and even some more advanced education does
not prepare you to such strange effect. Indeed, everything in electrostatics and electromagnetics
lead you to believe that to have some action (aka movement) you need reaction. If you
pull something with magnet, something pulls on the magnet. Opposite charges attract each other,
same charges repulse each other - but always there are two partners involved. But here - both
electrodes go together!
So, there are two questions
- Is it true?
- How the heck can it be?

First question is answered by more then 200 replicators around the world.
Everybody can actually make Lifter by themselfs, using simple and clear
assembly instructions by J. Naudin.

Second question is answered in great detail by this web-site.
See "how does it work" for simple explanation of effect, and for
set of equations "modeling toolbox" which you can use
to see how much thrust you can get at given voltage, current, distance
between electrodes etc.
     For these who don't believe assertions and want mathematical proofs
(as it is good idea to be) there is a collection of articles with exact derivations,
references, comparissons with experimental data, and modeling analysis
in order to improve performance. Lots of common questions about different effects
associated with lifter are addressed in Lifter FAQ.
     Finaly, any good theory should allow to get better designs. New design proposals
and instructions (including numerical parameters) have been based on this
theory and have already shown promice by experimentators worldwide.