How Many Electrons are Needed to Create a Force of 10^-19 N Between Two Spheres?

AI Thread Summary
To determine the number of electrons needed to create a force of 10^-19 N between two spheres 3 cm apart, the equation F = k(q^2/r^2) is used. The calculated charge (q) is found to be 1x10^-16 N, leading to the conclusion that n equals 625 electrons when using q = ne. However, the book states the answer is 25 electrons, prompting a request for clarification on the discrepancy. The consensus indicates that the calculation of 25 electrons does not yield the required force of 10^-19 N. Therefore, the correct number of electrons needed is indeed 625.
lionel messi.
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1. Homework Statement :
the excess(equal in number) of electrons that must be placed on each of two small spheres spaced 3 cm apart, with force of repulsion between the spheres to be 10^-19N, is...?


3. The Attempt at a Solution :
since,
f=kq^2/r^2.
ive calculated q from here which is 1x10^-16N..
then used,
q=ne..
from here n becomes 625 electrons. but answer in my book is 25 electrons.can someone point out my mistake?
 
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Your answer is correct, 25 electrons does not give 10^-19 N.
 

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