In figure ( a ), a particle of elementary charge + e is initially at rest at coo
ID: 3308935 • Letter: I
Question
In figure (a), a particle of elementary charge +e is initially at rest at coordinate z = 40 nm on the dipole axis through an electric dipole. (The origin of z is at the dipole center.) The particle is then moved along a circular path around the dipole center until it is at coordinate z = 40 nm. Figure (b) gives the work Wa done by the force moving the particle versus the angle that locates the particle relative to the positive direction of the z axis. What is the magnitude of the dipole moment?
(in C · m)
Explanation / Answer
potential due to dipole
V = p cos(theta) / (4 pi e0 r^2)
initially theta = 180 then finally theta = 0
delta(V) = ( p / 4 pi e0 r^2) (cos0 - cos180)
= p / ( 2 pi e0 r^2)
Work done = - q delta(V)
-6 x 10^-30 = (-1.6 x 10^-19) (p) / (2 x pi x 8.854 x 10^-12 x (40 x 10^-9)^2)
p = 3.34 x 10^-36 C m