PH113
Physics III
Test II
Spring 1998/99
Name _________________________
(Please print in UPPER CASE BLOCK
letters)
No books or written notes are allowed. You may use the formula sheet provided, your laptop and
any resources residing on your hard drive. This includes Maple and Working Model. No
network connections are allowed. Any student with a physical connection between the computer
and the network outlet during the test will receive a zero on the test.
Show all your work. No credit will be given for answers appearing without supporting
calculations. Partial credit may be awarded based on clarity and completeness of solution. Maple
calculations (but not Working Model) will be accepted as part of the test paper but must be
handed in on the 3 ½ inch diskette provided by the instructor. All Maple code must be
commented for clarity the same as hand calculations.
1. In order to test the effect of magnetic fields on squirrels, alien invaders construct a solenoid
8.00 m long and 8.00 m in radius. The resulting solenoid has an inductance of 500 H.
(a) How many turns does the solenoid have? [Hint: more than 8.]
(b) If the solenoid is supplied with 2.5 MA (2.5 x 106 A) of current, what will be the magnetic
field inside the coil? [Note if you didn’t get part (a), use N = 4000 and proceed.)
(c) The aliens’ power supply can has an EMF of “only” 20,000 V. What is the shortest length of
time over which the current in the coil can be raised from 0 A to 2.5 MA? [Ignore the coil
resistance.]
PH113
Physics III
Test II
Spring 1998/99
Page 2 of 4
Initials _______________
(Please use BLOCK letters)
2. Two circular parallel capacitor plates are 3.00 mm in radius. A uniform electric field E exists
between the plates as shown in the diagram. Because the E-field is changing in time, a magnetic
field of magnitude B = 2.00 x 10-7 T exists along the circular path of radius 6.00 mm shown as a
dotted line in the figure.
(a) What is the magnitude of the circulation integral
Š B@dl around the circular path indicated by the
dotted line?
(b) Find the magnitude of dE/dt.
(c) If the E-field is increasing in strength in the direction shown, indicate with arrow heads the
direction of the B-field around the dashed line in the diagram.
PH113
Physics III
Test II
Spring 1998/99
Page 3 of 4
Initials _______________
(Please use BLOCK letters)
3. A carbon arc acts as a light source emitting 0.80 kW of optical power isotropically (in all
directions equally).
(a) What is the irradiance (your book would say “intensity”) at a distance of 5.0 m from the
source?
(b) What is the radiation pressure acting on a perfectly absorbing object 5.0 m from the source?
(c) What force acts on a perfectly absorbing rectangular sheet of paper with dimensions 10. cm x
12. cm held so that it is facing the source at a distance of 5.0 m?
(d) If a sheet polarizer is placed between the source and the paper, what will be the force on the
paper? (Note: If you didn’t get part (c), use 20 N, and proceed with the parts (d) and (e).)
(e) If a second polarizer is inserted between the source and the paper with its polarization axis
rotated 36.87E from the first polarizer, what will be the resulting force on the paper?
PH113 Physics III
Test II, Spring 1998/99
Page 4 of 4
Name _______________
(Please use BLOCK letters)
4. A point source of light emitting in all directions is located 80.0 cm below the surface of a body
of water (n = 1.33).
(a) On the diagram at the right
draw the path of the two rays
shown after they encounter the
surface of the water. Label any
angles that describe the rays’
subsequent paths, and calculate
those angles in the space below.
(b) Find the diameter of the circle at the surface through which light emerges from the surface of
the water.