Michel Jullian wrote: > > ----- Original Message ----- > From: "Harry Veeder" <[EMAIL PROTECTED]> > To: <vortex-l@eskimo.com> > Sent: Sunday, February 04, 2007 2:01 AM > Subject: Re: [Vo]: Re: Fred's Van de Graaff Antics > > >> Michel Jullian wrote: >> >>> Sure Harry it's ion wind. Naudin's comment, athough somewhat misleading, is >>> correct too. The collector (bottom negative armature) is indeed attracted >>> upwards to the "parachuting" positive ion cloud _generated by_ the corona >>> wire >>> (the ion cloud, dragging ambient air along, is pulled downwards with an >>> equal >>> and opposite force, hence the wind). This upwards pull constitutes most of >>> the >>> lift, because most of the positive charge (whose total value is equal and >>> opposite to the collector's negative charge due to charge conservation) is >>> in >>> the air, so the wire itself carries a comparatively small positive charge, >>> so >>> it's contribution to the lift (upwards push from the positive ion cloud >>> below) >>> is comparatively small. >>> >>> Same reasoning holds if you reverse polarity, in all cases you get thrust in >>> the direction from the collector to the wire (not necessarily upwards BTW). >>> >>> Michel >> >> >> >> For sake of argument assume there is no ion wind. What you have >> are two oppositely charged bodies where one (the wire) is above the other >> (the tube). Each will be attracted to the other. The tube will accelerate >> upwards and the wire will accelerate downwards. If the attractive forces are >> opposite AND equal the lifter will not take off, but since tube has some >> freedom to move it will rise until it is stopped by the cross member. > > If the force is sufficient, yes. > >> However, if these forces are opposite but not equal the lifter will either >> want to ascend or descend depending on the polarity. > > If there is no ion wind there are no positive charges in the air so they are > all on the wire, so the forces are necessarily equal. The thing becomes an > ordinary capacitor, it doesn't fly. > >> On the other hand if an ion wind is the cause of this net force then it >> should be possible to reduce the net force by inserting a horizontal neutral >> (e.g. paper) shield in the gap between the wire and the tube. This shield >> would be fixed to the struts of the lifter. > > Sure, but why reduce the net force? > > Michel
This tests the ion wind hypothesis. Is the hypothesis sufficient to explain the motion of the lifter? If the lifter still rises then it is insufficient. Harry
