77777
77777
Instructor: P. Kumar
PHYSICS DEPARTMENT
PHY 2049
Midterm III
July 20, 2007
Signature:
Name (print, last first):
On my honor, I have neither given nor received unauthorized aid on this examination.
YOUR TEST NUMBER IS THE 5-DIGIT NUMBER AT THE TOP OF EACH PAGE.
DIRECTIONS
(1) Code your test number on your green answer sheet (use 76–80 for the 5-digit number). Code your name
on your answer sheet. Darken circles completely (errors can occur if too light). Code your student number on
your answer sheet.
(2) Blacken the circle of your intended answer completely, using a number 2 pencil. Do not make any stray
marks or the answer sheet may not read properly.
(3) The answers are rounded off. Choose the closest to exact. There is no penalty for guessing.
>>>>>>>>WHEN YOU FINISH <<<<<<<<
Hand in the green answer sheet separately.
1. In the figure, a beam of light, with intensity 35 W/m2 and polarization parallel to a y axis, is sent into a system of two polarizing
sheets with polarizing directions at angles of θ1 = 66◦ and θ2 = 90◦
to the y axis. What is the intensity (in Watts/m2 ) of the light
transmitted by the two-sheet system?
(1) 4.83
(2) 0
(3) 14.23
(4) 10.23
(5) none of these.
2. Light with an intensity of 1kW/m2 falls normally on a surface with an area of 1 cm2 and is completely reflected. The
force of the radiation on the surface is:
(1) 6.7 × 10−10 N
(2) 1.0 × 10−4 N
(3) 3.3 × 10−11 N
(4) 1.7 × 10−10 N
(5) 3.3 × 10−10 N
3. An arrangement for generating a traveling electromagnetic wave in the shortwave radio region of the spectrum works
as follows: an LC oscillator produces a sinusoidal current in the antenna, which generates the wave, traveling outward
at the speed of light. What is the wavelength (in meters) of the wave emitted by this system if L = 0.323µH and
C = 45.0pF?
(1) 7.19 m
(2) 1.14 m
(3) 719 m
(4) 114 m
(5) None of these
4. A 1-µF capacitor is connected to an emf that is increasing uniformly with time at a rate of 100 V/s. The displacement
current between the plates is:
(1) 1 × 10−4 A
(2) 0
(3) 1 × 10−8 A
(4) 1 × 10−6 A
(5) 100 A
5. A current of 1A is used to charge a parallel plate capacitor with square plates. If the area of each plate is 0.6m2 the
displacement current through a 0.3m2 area wholly between the capacitor plates and parallel to them is:
(1) 0.5A
(2) 1A
(3) 2A
(4) 0.7A
(5) 0.25A
77777
77777
6. Please make sure that you have inserted your exam code in spaces 76-80 on the scantron sheet. Also that you have
put in your name, UF ID and you have signed the scantron sheet at the back.
(1)
(2)
(3)
(4)
(5)
I have already done all.
Please dont bother me I am taking an exam.
What is a scantron sheet.
What is an exam code.
None of these
7. A charged capacitor and an inductor are connected in series. At time t = 0 the current is zero, but the capacitor is
charged. If T is the period of the resulting oscillations, the next time after t = 0 that the energy stored in the magnetic
field of the inductor is a maximum is:
(1) T/4
(2) T
(3) T/2
(4) none of these
(5) 2T
8. An LC circuit has an inductance of 15mH and a capacitance of 10µF. At one instant the charge on the capacitor is
25µC. At that instant the current is changing at the rate of:
(1) 170A/s
(2) 0
(3) 1.7 × 108 A/s
(4) 5.9 × 103 A/s
(5) 3.8 × 102 A/s
9. An RLC series circuit has R = 4Ω, XC = 3Ω, and XL = 6Ω. The impedance of this circuit is:
(1) 5Ω
(2) 7Ω
(3) 9.8Ω
(4) 13Ω
(5) 7.8Ω
10. Suppose this page is perpendicular to a uniform magnetic field and the magnetic flux through it is 5Wb. If the page
is turned by 30 degrees around an edge, the flux through it will be:
(1) 4.3Wb
(2) 2.5Wb
(3) 5Wb
(4) 5.8Wb
(5) 10Wb
11. A long straight wire is in the plane of a rectangular conducting
loop. The straight wire carries a constant current i, as shown.
While the wire is being moved toward the rectangle the current in
the rectangle is:
(1)
(2)
(3)
(4)
(5)
counterclockwise
zero
clockwise
clockwise in the left side and counterclockwise in the right side
counterclockwise in the left side and clockwise in the right side
12. A cylindrical region of radius R contains a uniform magnetic field, parallel to its axis, with magnitude that is changing
linearly with time. If r is the radial distance from the cylinder axis, the magnitude of the induced electric field outside
the cylinder is proportional to:
(1) 1/r
(2) R
(3) r
(4) r2
(5) 1/r2