Download Special Techniques

Special Techniques
By: Jay Pandya
1. A dipole p is placed radially at a distance d from the
centre of a grounded conducting sphere of radius
r(<d).What is the magnitude of dipole moment
compared to p ?
a) More
b) Less
c) Equal
2. Certain charge is distributed over a circle according to
the law q = q0cost where q is the surface charge density
and t is the angle measured from the x axis. What
is direction of total dipole moment?
a) Along x axis
b) Along y axis
c) Along the line y=x
d) Along the line y=-x
3. Two charges q1 and q2 are placed at (0,0,a) and (b,0,0)
respectively. Find the average potential due to both the
charges over the surface of a sphere of radius r (<a<b)
which is centred at origin.
a) kq1/a
b) kq2/b
c) kq1/a + kq2/b
d) kq1/b + kq2/a
4. For the above problem if a<r<b what is the average
potential over the surface of sphere?
a) kq1/a + kq2/b
b) kq1/r + kq2/b
c) kq1/a + kq2/r
d) kq1/r + kq2/r
5. The potential of four charges q(0,0,d) , 2q(d,0,0) ,-q
(0,0,-d) , -2q(-d,0,0) will have the major contribution from
which multipole term
a) Monopole term
b) Dipole term
c) Quadrupole term
6. Two charges q & 2q placed at a distance d and 2d
respectively from a grounded conducting plane. What is
magnitude of force experienced by the charge q?
a) 2kq2/d2
b) 2kq2/d2 + kq2/(2d)2
c) 2kq2/d2 + kq2/(2d)2 + 2kq2/(3d)2
d) None of these
7. A charge q is placed at a distance d from the centre of a
grounded conducting spherical shell of radius r(<d) .
What is the force experienced by the charge q?
8. Prove using uniqueness theorem that electric field in
an empty cavity of a conductor is zero.
9. If a point charge q is held a distance d above a
grounded conducting plane then what is the potential in
the region above the plane?