Re: Scotch tape, was Re: Curvature of Space

[John Gastineau <gastineau@mindspring.com>]

At 05:35 PM 2/20/98 -0400, Ludwik wrote:
> Sorry for replying under wrong thread. 

You didn't--I changed it in my last message. The topic has drifted
considerably. 

I was referring to the thickness of
> the neutral tape to which the electrified tape is attracted. Can I say a
> *charged' tape this time?

The attraction should depend on the amount of neutral material, yes. A
quickie experiment on my desktop shows that as you increase the amount
of neutral material, the force on the tape increases. 

The thickness of the charged tape is immaterial, as the charge is on
the surface. 

The first homework problem in C&S is to use your knowledge of
mechanics, assume Coulomb's Law, and now devise and perform a
measurement of the charge density on your tape. (the mass per unit
length of tape is given) Absolutely wonderful exercise to give students. 

The remarkable thing is that with pretty crude experiments, students
all get within a factor of five or ten of one another. 

JEG

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