atomic perspective?

What is the force between a point charge of 0.1 mC located at a distance of 1m from an infinite wire whose charge density is 1nC/m (n = nano = 10^-9)? If the distance is now 2m, what is the force?

In the Millikan oil drop experiment, the charge of an electron is measured by placing an ionized oil drop of mass, m, and net charge, e, between the conducting plates of a parallel plate capacitor that produces a vertically downward electric field as shown in the diagram below. If the electron is in static equilibrium between the plates, which of the following is the correct expression for the electron charge of magnitude e? The voltage difference between the capacitor plates is V and the distance between the plates is d.                                                                                                   a. V/(mgd)   b. mgV/d   c. d/(mgV)   d. Vd/mg   e. mgd/V

Charge! Suppose two phosphate groups in DNA (eachwith a charge of -1) are separated by 12 Å. What is theenergy of the ionic interaction between these two phosphates assuming a dielectric constant of 80? Repeat thecalculation assuming a dielectric constant of 2.