Re: First EM lab

[Bernard Cleyet <anngeorg@PACBELL.NET>]

Joe Heafner wrote:

> > From: Brian Whatcott <inet@INTELLISYS.NET>
> >
> > Seems like this old cynic from NooYork and this old cynic from Altus are
> > going to have to go along with the hints so far.
> > That an electric force is capable of lifting off a confetto at a particular
> > distance.
> Rip up a piece of paper and see for yourself. Don't take my word for it.
>
> > We are to choose an inverse square law (assuming the point of a plastic
> > pen) rather than an inverse law for an expanse of Scotch tape.
> >   And we have been given some suggestion about the likely charge density on
> > the complex starch of which we speak. I suppose we need to measure the mass
> > of the confetto - can it be more than 0.1 mg?   My balances will not
> > directly measure
> > so small an item. Perhaps  measure a toilet roll? That's just too indirect....

more direct than much physics these days (possibly more accurate than using an
analytic balance -- the error will be in measuring the area of the piece of tissue)
this method is considerably more accurate than using a micrometer for find the areal
density of foils for radiation absorption expts.  -- or the thickness of gold leaf.
for an electroscope.

> >
> Can't you just estimate the piece of paper's mass?
>
> Is the inverse square force law valid for all charged objects?

I've already given the formula for a "point" charge and a dipole, etc.

bc



> Cheers,
> Joe
>
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