(Forces on a dipole): You may wonder if one can exert an electrostatic force on

ID: 2126432 • Letter: #

Question

(Forces on a dipole):

You may wonder if one can exert an electrostatic force on an electric dipole, which is

overall neutral. To investigate this, suppose you have a NaCl molecule (electric

dipole) and a proton (p) with charge +q = e = 1.6x10-19 C lined up the way it is shown

below, so the Clion is a distance R from the proton and the Na+

ion is a distance R+d from the proton.

1) Write down a formula for the magnitude of the net electrostatic force on the dipole

by the proton. If the magnitude is not zero, is it an attractive or a repulsive force?

Briefly explain.

2) Now assume R = 1 mm and calculate the magnitude of the net electrostatic force

on the dipole by the proton.

3) Next, calculate the magnitude of the electrostatic force on the proton by the

dipole. Is the magnitude of this force larger than, smaller than or equal to the net

force you found in part 2)? Which physical principle justifies your answer? Physics 2020, Fall 2013 page 2 of 2

University of Colorado at Boulder, Department of Physics

4) Suppose in our arrangement we rotate the NaCl molecule by 180 degrees. Thus,

now the proton is a distance R from the Na+

ion and a distance R+d from the Clion. Would the magnitudes and directions of the electrostatic forces change,

which you calculated in parts 2) and 3)? Why or why not?

force acting on dipole creates the torque given by T = p X E or pEsin theta

where p = 2aq

b. Ef due to dipole E = p/4pie0 R^3

force F = Eq = 2aq^2/4pie0 SINCE R=1

C. SAME AS THAT PART b

D. MAGNETUDE LL REMAIN SAME BUT DIECTION WILL BECOME OPPOSTE TO THTA OF EARLER PATH

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.