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Re: Coulomb's force lab



Hello Michael;

Not only did I recover the factor of four this morning;
I also discover something that you, and other users of
Coulomb's torsion balance, may find useful.

1) The factor of four was easy, it was the matter of
connecting the ground (at the back of the power supply)
to the negative kV terminal. I was assuming that the
connection already existed inside the unit. The manual
is clear that either + or - should be grounded but I did
not pay attention.

2) And here is something useful to know. I touched
each sphere with the 6 kV wire when it was partially
surrounded by a grounded cylinder (a soup can). As
expected, this resulted in larger Q1 and Q2. The
force doubled for the same distance.

Why is this important? Because F (in arbitrary units)
can now be measured more accurately than before.
In other words, one can avoid distances < 6 cm at
the B correction becomes significant, and still cover
a wide range of distances. Avoiding the B correction
is desirable because its derivation is not trivial. It has
to do with the redistribution of Q1 and Q2 on two
conducting spheres which are close to each other.
Nothing profound but perhaps useful.
Ludwik Kowalski