A sphere of radius R has a uniform volume charge density ρ in addition to a surface chare density σ = σ0sin2θ. Find the potential Φ(r) everywhere outside of the sphere.
Hint:
P0(x) = 1
P1(x) = x
P2(x) = (3x2 - 1)/2
P3(x) = (5x3 - 3x)/2
A small conducting ring of radius a is located in the xy-plane centered at
the origin. A positive charge Q is place on the ring.
(a) Find the potential Φ on the z-axis at z > a and expand your
expression in powers of a/z.
(b) The potential Φ(r,θ) at a arbitrary points in space with r >
a can be
expanded in terms of Legendre polynomials, Φ(r,θ) = ∑n=0∞[Anrn
+ Bn/rn+1]Pn(cosθ).
Find the expansion coefficients.
An electron at a distance d = 1 mm is projected parallel to a grounded
perfectly conducting sheet with an energy of 100 electron volts. Let the
grounded conducting sheet lie in the xy-plane and the initial velocity of the
electron point in the x-direction. Let z(0) = d.
(a) Find the z-component vz of the electron's velocity as a
function of its distance z from the sheet.
(b) Find the distance that the electron travels until it hits the plate.
Neglect the force of gravity.
(c) Find the magnitude and direction of a magnetic field parallel to the
surface of the plate and perpendicular to the electron velocity that keeps the
electron from hitting the plate.
Give numerical answers for parts (b) and (c).
Hint: z = dsin2θ may be a useful change of variable. ∫sin2θ dθ
= θ/2 - sin(2θ)/4.
Assume in a region of space the electric field E lies in the (x,y)
plane and is rotating with frequency ω counterclockwise about the z-axis.
At t = 0, E = E0 i. Assume ω is small and induced
magnetic fields can be neglected.
(a) How could you produce such an electric field?
(b) Find general solution for x(t), y(t), vx(t) and vy(t)
for a particle with mass m and charge q located in that region of space?
(c) Is it possible for the particle to stay confined in that region of
space? What initial conditions are required?
The displacement vector from electric dipole p1 to dipole p2 is
r.
(a) Calculate the electric potential energy W.
(b) Calculate the force F21 that p1 exerts on
p2.
(c) Calculate the torque τ12 that p1 exerts on
p2.
(d) Let p1 = (10-9 Cm)k be located at
the origin and p2 = (10-9 Cm)i at r =
(3 m)i + (4 m)k.
Provide numeric answers for F21 and τ12.