This preview shows pages 1–3. Sign up to view the full content.
Final Exam: Graduate Electromagnetics I, 95.657
Fall 2011, UMass Lowell, Dr. Baird
Part I: Multiple Choice (30 Points)
Circle only one answer to each question. In cases where many answers may seem true, choose the one
best answer.
1. The current
I
runs through an arbitrarilyshaped loop of thin wire. How does the magnetic field
strength
B
produced by this system depend on
I
?
(a)
B
is proportional to
I
2
(b)
B
is proportional to
I
(c)
B
does not depend on
I
(d)
B
is proportional to cos(
I
)
2. An electric charge distribution is given by:
ρ=
Q
4
π
R
3
sin
(
5
r
R
)
e
−
(
r
R
)
2
cos
3
θ
where
R
is some constant radius,
Q
is some constant charge,
r
is the radial dimension of spherical
coordinates and
θ
is the polar angle of spherical coordinates. If we were to solve for the electrostatic
potential created by this charge distribution, what kind of functions would the final solution involve?
(a) complex exponentials
(b) Bessel functions
(c) ordinary Legendre polynomials
(d) spherical harmonics
3. In magnetostatics, which one of the potential definitions is valid,
B
=∇×
A
or
B
=−∇ Ψ
M
?
(a) only
B
=∇×
A
(b) only
B
=−∇ Ψ
M
(c) Both
B
=∇×
A
and
B
=−∇ Ψ
M
are valid all the time
(d)
B
=∇×
A
is valid all the time, but
B
=−∇ Ψ
M
is only valid when there is no total current
4. Which expression describes electromagnetic field energy
flow
?
(a) ½(
E
•
D
+
B
•
H
)
(b)
E
×
H
(c)
E
×
D
(d)
J
•
E
5. What does the surface of a
diamagnetic
material tend to do to a preexisting external magnetic field?
(a) nothing
(b) repels and dilutes magnetic field lines
(c) attracts and concentrates magnetic field lines
(d) knots up the field lines
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document6. When we solved for the potential of a point charge outside a conducting sphere using the method of
images, where did we place the image charge(s)?
(a) one image charge was placed in the sphere on the line connecting the real charge with the sphere's
This is the end of the preview. Sign up
to
access the rest of the document.
 Fall '11
 Staff
 Current, Mass

Click to edit the document details