Final Exam Review
Supplemental Instruction
Iowa State University
Leader:
Course:
Instructor:
Date:
Rosalie
Dubberke
Prozorov
12-13-2015
These are the questions for the final exam review on the 13th. They are in the same order as I
have them in my powerpoint solution, and we will go through them together. Feel free to ask
questions as we go and work with the people around you!
1) Two point charges, +q and (unknown) Q produce the net electric field shown at point p in
the figure. What is the charge Q in terms of q?
2) Two uncharged metal spheres are touching. A third, positively charged sphere is placed
to the left of sphere 1. With this third sphere still in place, spheres 1 and 2 are moved
away from each other so that they are no longer touching, and the third sphere is
removed. What are the charges on spheres 1 and 2?
1
2
3
3) An uncharged conductor has a hollow cavity inside of it. Within this cavity, there is a
charge of +10 C that does not touch the conductor. There are no other charges in the
vicinity. What are the charges of the inner and outer surfaces of the conductor?
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4) The figure shows three chargers labeled 𝑄1 , 𝑄2 , 𝑎𝑛𝑑 𝑄3 , and electric field lines in the
region surrounding the charges. What are the signs of these charges?
5) A solid metal ball of radius 2.0 cm carries a total charge of -0.1 μC. What is the
magnitude of the electric field at a distance from the ball center of 1.0cm?
6) When two point charges are a distance d part, the electric force that each one feels from
the other has magnitude F. In order to make this force twice as strong, what would the
distance have to be changed to?
7) A point charge 𝑞1 = 3.8 𝑛𝐶 is located on the x-axis at x = 2.1 m, and a second point
charge 𝑞2 = −6.2 𝑛𝐶 is on the y- axis at y = 1.15 m. What is the total electric flux due to
these two point charges through a spherical surface centered at the origin with radius r =
1.55 m?
8) A small metal rod has a mass of 0.1 kg and it lies in a magnetic field of 1 T. If the rod is 1
m long and carries a current, what current is necessary so that the net force on the rod is
zero?
9) A 1 m by 1 m circuit containing only a 50 Ω resistor lies perpendicular in a magnetic
field. The magnetic field changes from 5 T to 1 T in 30 ms. What is the magnitude of the
induced current?
10) What is the net flux through a cube of side 10 cm if a + 2 C point charge is placed 20 cm
from the center of the cube?
11) An electron moving with a velocity = 5.0 × 107 m/s enters a region of space where
perpendicular electric and magnetic fields are present. The electric field is E = 1j. What
magnetic field will allow the electron to go through the region without being deflected?
12) Consider a fully-charged parallel plate capacitor. The capacitor is far from other objects
and is not connected to a battery. The plates are now being pulled apart. What happens to
the potential difference between the plates as they are being separated?
a) It decreases
b) It increases
c) It remains constant
d) It is zero
e) Cannot be determined from given information
13) Two resistors of 15 and 30 Ω are connected in parallel. If the combination is connected in
series with a 9.0-V battery and a 20-Ω resistor, what is the current through the 15-Ω
resistor?
14) A series LR circuit consists of a 2.0-H inductor with negligible internal resistance, a 100ohm resistor, an open switch, and a 9.0-V ideal power source. After the switch is closed,
what is the maximum power delivered by the power supply?
15) In a series LRC circuit, the frequency at which the circuit is at resonance is 𝑓0 . If you
double the resistance, the inductance, the capacitance, and the voltage amplitude of the ac
source, what is the new resonance frequency?
16) If you have 2 circuits each connected to a 120 V power source and each containing 3
bulbs of resistance 20 Ω (one circuit has the three bulbs in parallel and the other has the
bulbs in series), which bulbs will glow the brightest? What is the power delivered to each
bulb?
17) Which one of the phasor diagrams shown below best represents a series LRC circuit
driven at resonance?
18) An electromagnetic wave with frequency 64 Hz travels in an insulating magnetic material
that has dielectric constant 3.64 and relative permeability 5.18. At this frequency, the
electric field has amplitude 7.2 V/m. Determine the speed of propagation of the wave, the
wavelength, and the amplitude of the magnetic field.
19) A laser emits 1.00 mW of average light power in a cylindrical beam of radius 5.00 mm.
The intensity of the light at a point in the beam is ____ W/m2
20) A beam of unpolarized light of intensity I0 passes through a series of ideal polarizing
filters with their polarizing directions turned to various angles as shown in the figure.
What are the intensities at points a and b?
21) In experiment RR – Reflection and refraction, you used the set up shown in the figure
below. A monochromatic laser beam is incident onto the flat side of a semi-circular
prism, right at its center. The orientation angles of the flat side of the prism (α) and of the
refracted ray (β) are measured relative to the direction of the incident ray. For the first
orientation you try, α = 37° and β = 155°. For a good measurement of the index of
refraction, we will have to get many more measurements, but we can use the first one to
obtain a rough estimate. Based on this first measurement, what is the index of refraction
of the material?
22) A dentist uses a curved mirror to view teeth on the upper side of the mouth. Suppose she
wants an erect image with a magnification of 2.00 when the mirror is 1.25 cm from a
tooth. (Treat this problem as though the object and image lie along a straight line.)
Determine what kind of mirror is needed using a ray diagram, and determine the focal
length and radius of curvature of the mirror
23) Draw a lens diagram for the following lenses and define the images
24) Consider an object with s = 12 cm that produces an image with s’ = 15 cm.
• Find the focal length
• Tell whether the image is real or virtual
25)
A converging lens has a focal length f. An object is placed at a distance between f and 2f on a
line perpendicular to the center of the lens. The image formed is located at what distance
from the lens?
A) between the lens and f
B) f
C) 2f
D) Farther than 2f
E) Between f and 2f
26) A glass converging lens has one flat side and one side with a radius of curvature of 20.0
cm. The focal length of the lens is ____ cm. (The index of refraction of the glass in the
lens is 1.50)
27) In a double slit experiment, if the slit separation is increased, which of the following
happens to the interference pattern?
28) A man stands in the exact center of a glass freight car moving at very high speed. He
holds a flashlight in each hand and directs them at opposite walls, switching them on at
the same time. You stand still outside of the freight train and watch it go by. In the mans
frame of reference, which beam of light travels faster? In your frame of reference which
beam of light travels faster? In the mans frame of reference which wall is struck by light
first? In your fram of reference which wall is struck by light first?
29) A star is moving towards the earth with a speed at 90% of the speed of light. It emits
light, which moves away from the star in every direction at the speed of light, c. Relative
to us on earth, what is the speed of light moving toward us from the star?
30) If the accuracy in measuring the position of a particle increases, the accuracy in
measuring its velocity will do what?
A) increase
B) remain the same
C) decrease
D) it is impossible to say since the two measurements are unrelated and do not affect each
other