8/12 Question 3 in our HW for The Electromagnetic Spectrum
initially had programming errors in parts (c) and (d).
The correct answers are one-quarter of a wavelength
(for c) and one-quarter of a period (for d), but the
programming was initially accepting the INCORRECT
answers of one-half of a wavelength and one-half of a
period. The correction was made at 1:30 PM on MON and
the problem was regraded between 1:40 and 1:45. The
problem will be regraded again on TUE, and no penalties
will be assessed on this problem for any incorrect
responses. I apologize for any stress the errors may
have caused. Thanks. GBA
8/09 I neglected to give the ungraded HW for today; here
it is. Show that (1/mu_0)*the time average of (the
radiated vector E field at location r cross product
the radiated vector B field at the same location)
yields the radiated intensity at that location with
the direction of propagation of the EM radiation
attached; i.e. show that
(1/μ0)*<
Erad(r,t)
× Brad(r,t)> = c*0.5*ε0*(Erad,max
(r))2
with the direction of propagation attached on the
right-hand side.
8/08 Because of an error in Serway's 8th edition, some
students who use Serway rather than the notes for
reference had trouble with the AC Circuits HW. As
a result, the AC Circuits HW has been reopened until
9:59 PM THUR night. Thanks. GBA
8/05 The fourth question in the WebAssign HW for 8/5
initially had an error in its text for Parts (a)
and (d); it originally had the words "absolute
value" where the correct text was "maximum value".
This error was corrected at 11:20 AM on MON 8/5.
If you opened your HW before this time, be sure
to reload the page to see the correct text.
Thanks. GBA
7/28 The due date for the Ampere's Law HW has been
extended until 9:59 PM MON 7/29. Many students
reported that they had trouble with question 6 in
HW 15. As a result, a figure has been added to the
question, and the due date for the HW has been
extended from SUN night until MON night.
Thanks. GBA
7/25 Because we ran out of time, I was unable to give
you today's ungraded HW; here it is. The figure
for this ungraded HW is here; two separate situations
are drawn in the figure. Use Biot-Savart to show
that the B field strength at the center of the
quarter-circle of current is (mu_0*I)/(8*R). And
for the right- hand picture, show that the B field
strength at P due only to the current segment of
length L is (mu_0*I*L)/(4*pi*x_0*sqrt(L^2+x_0^2))
Thanks. GBA
7/25 The first question in the WebAssign HW for 7/25
initially had an error in its text (it originally
incorrectly identified side bc as being the short
side). This error was corrected at 11:15 AM on
THUR 7/25. If you opened your HW before this time,
be sure to reload the page to see the correct text.
Question 1 will be regraded on FRI morning and no
points will be deducted for answers that were not
accepted for question 1. Thanks, and I apologize
for any confusion that might have been caused by
the initially incorrect text. GBA
7/22 Because we ran out of time, I was unable to give
you today's ungraded HW; here it is. The figure
for this ungraded HW is here. A voltmeter
(represented here by a circle with a V inside) is
an ammeter with a large resistance; the voltmeter
reading is simply the voltage across this resistance.
For the three possible values of the voltmeter
resistance given in the table below, show that the
voltmeter reading is given by the corresponding
value in the table. Thanks. GBA
R_V Meter Reading
50 kOhms 57.0 V
250 kOhms 68.6 V
1000 kOhms 72.1 V
7/19 In Question 2 from HW#11 for Current and
Resistance, the numerical values of the radius
for Part (a) were initially presented incorrectly.
This presentation error was corrected at 11:15 AM
on FRI 7/19. If you opened this question before
that time, be sure to reload the page so that you
will see the correct numerical values for Part (a).
Because this presentation error may have caused
some confusion, the due date for HW#11 has been
extended until MON night at 9:59 PM. Thanks, and
I apologize for any confusion the presentation
error may have caused. GBA
7/19 There was a bug in the programming of the answers
to Question 4 (Geiger Counter) in our WebAssign
HW#10 for Dielectrics. I apologize for any
stress caused by this programming error. The
error was corrected at 10:38 AM FRI 7/19 and
the HW#10 has been reopened until SUN night at
9:59 PM. Many thanks to the alert student who
pointed out the programming error. The question
will be regraded by WebAssign on MON morning,
and no points will be deducted for unaccepted
answers. GBA
7/18 Please download the Definitions for Current and
Resistance from our class webpage. Please print
these 2 pages and bring them with you to lecture
on FRI 8/18. Thanks. GBA
7/17 There was a typo in TUE night's HW in question 6(c).
The question should have asked for the y-component
of the electric field (that is what is given by the
requested derivative); instead the question incorrectly
asked for the electric field strength. The HW has
been made available again until 9:59 PM WED night and
question 6 will be regraded on THUR morning. Thanks,
and I apologize for any confusion caused by this
typo. GBA
7/16 I neglected to give you the ungraded HW problem for
lecture 8 on TUE 7/16. Here it is:
A metal ball of radius a is concentric with a thin
metal shell of radius b. The charges are +Q on the
ball and -Q on the shell. By TWO methods, show that
for r bigger than a but less than b,
V(r) = kQ((1/r)-(1/b))
where V is with respect to zero as r goes to
infinity. GBA
7/12 In the HW for FRI 7/12, problem 1(d) originally
had missing text. The missing text was added at
11:55 AM on FRI. The text that had been missing
reads, " Calculate the torque about the midpoint
of the dipole," i.e. you are to assume that the
center of mass of the dipole is at its midpoint.
Thanks, and I apologize for any confusion this
missing text might have caused. GBA
7/07 There was a bug in the programming of the answer
to Question 6(b) in our WebAssign HW#2. WebAssign
was originally accepting the magnitude of the E
field at the relevant point in space rather that
the x-component of the E field at that point in
space. I apologize for any stress caused by this
programming error. The error was corrected at
2:33 SUN 7/7 and the question will be regraded by
WebAssign between 2:40 and 2:45. Many thanks to
the alert student who pointed out the programming
error. GBA
7/05 I neglected to give you the ungraded HW problem
for lecture 2 on FRI 7/5. Here it is:
Show that the electric field at the center of a
charged quarter circle (i.e. one fourth of a
charged ring -- the point of interest is at the
center of the ring), having radius R and charge
per unit length lambda, has magnitude given by
sqrt(2)*k*lambda/R.
7/04 There are several corrections to the printed
version of the syllabus. The MC tests this
summer will have about 12 questions, instead
of the 15 questions as written on page 5.
Also, the weighting of the MC part of our tests
will be 40% instead of 45%, and the weighting
of our lecture quizzes will be 40% instead
of 35%. Thanks. GBA
7/01 WebAssign registration opens at 12:01 AM
TUE July 2nd. Please follow the instructions
on our WebAssign Information webpage.
Thanks. GBA
5/08 No Updates Yet