제출 2010년 3월 19일 (금) C319
1. Three point charges Q1 9 C , Q2 4 C , Q3 36 C are arranged on a straight line. The distance between Q1 and Q3 is 9cm. It is claimed that a location can be selected for Q2 such that each charge will experience a zero force. Find this location. 2. A line charge of uniform charge density
l
forms a circle of radius b that lies in the
xyplane in air with its center at the origin.
a) Find the electric field intensity E at the point (0, 0, h).
b) At what value of h will E in part (a) be a maximum? What is this maximum?
3. Determine the work done in carrying a
5 C charge from P1 ( 1, 2, 4) to
P2 (2, 8, 4) in the field E a x y a y x
a) along the parabola y 2x , and
2
b) along the straight line joining P and P2 .
1
4. A finite line charge of length L carrying uniform line charge density
l
is coincident
with xaxis.
a) Determine V in the plane bisecting the line charge.
b) Determine E from
l
directly by applying Coulomb’s law.
5. The polarization in a dielectric cube of side L centered at the origin is given by
P P0 (a x x a y y a z z ) .
a) Determine the surface and volume boundcharge densities.
b) Show that the total bound charge is zero.
6. The space between a parallelplate capacitor of area S is filled with a dielectric whose permittivity varies linearly from
1
at one plate (y=0) to
2
at the other plate
(y=d). Neglecting fringing effect, find the capacitance.
7. Three capacitors
1 C , 2 C , and 3 C are connected as shown in Figure across a
240volt source. Calculate the electric energy stored in each capacitor.
1F
2 F
3F
+

240(V)
8. A parallelplate capacitor of width w, length L, and separation d has a solid dielectric slab of permittivity
in the space between the plates. The capacitor is charged to a
voltage V0 by a