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Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
Thomas F wrote ...
Actually I am not charging anything. I just have two sheets of metal in a vertical plane, with 5kV DC connected,to them and spaced 6mm or so apart.I bring some light paper between the two plates ,but i don't see any movement at all.Let me see if I can increase the voltage and try some more.
The metal plates will be attracted to each other, and you should be able to measure that easily enough. If they are 10 cm square, and 6 mm apart in air with 5000 volts between them, I figure about 3 grams-force. As Bjorn hinted, the force goes up as the square of the electric field strength. Electrostatic voltmeters based on this principle will give the same reading for DC and AC voltages with the same RMS value.
18 kV would put you at about the limiting E-field in air at sea level, with about 40 grams-force. Magnet poles of the same area and 1 tesla field strength would have 10,000 times more attraction, which is why few practical motors are electrostatic.
One way to get the attractive force is to figure the energy stored in the parallel-plate capacitor, and divide that by the distance between the plates. It's the mechanical work that could be done if the plates were allowed to move together (with constant Q, same as constant electric field and constant force, not constant voltage!).
Back to moving bits of paper, a subject on which I am no expert.
Methinks that in a uniform E-field (between parallel plates), an uncharged insulating object won't be attracted to either plate. How would it choose a direction? But it will tend to polarize & align its long axis with the field. In a field gradient, such as in the vicinity of a convex electrode, it will move toward the stronger E-field. I think that common electrostatic demonstrations usually also involve moving insulators that -do- pick up a net charge.
Registered Member #503
Joined: Sun Nov 19 2006, 06:37PM
Location:
Posts: 59
Hi Bjorn,
That was an interesting video.Any place where more details are put up about it ?
Thanks Klugesmith.
Methinks that in a uniform E-field (between parallel plates), an uncharged insulating object won't be attracted to either plate. How would it choose a direction? But it will tend to polarize & align its long axis with the field.
Possibly in static electricity with a non conductor ,you can get only a unipolar charge, which attracts the paper.The problem is how to replicate this with a DC supply?
Hi HVChick , I think a 2" spark would be almost 50kV.
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Static electricity
