Physics 112 Midterm Exam Questions and Answers
Question 1
A positive particle begins at a position near a negative plate and ends at a position near a positively charged plate. Which
statement is most accurate?
Correct Answer
Work is done on the particle so that the particle will end with more energy.
Question 2
Resistors of 10 Ω, 20 Ω, and 40 Ω are all connected in parallel to a 12 V battery. What is the current through the 20 Ω
resistor?
Correct Answer
V = IR
(12 V) = I (20 Ω)
I = 0.6 A
Question 3
Two charged parallel plates have a uniform field strength of 1200 N/C between them. If the separation distance between
the plates is 0.15 m, what is the potential difference between the plates?
Correct Answer
Page 1 of 122
,Question 4
Two charged particles have opposite net charges. They are placed near each other, and released from rest. Which of the
following statements best describes the motion of the particles?
Correct Answer
The particles will accelerate towards each other with an increasing acceleration.
Since the charges are opposite, they will attract, and move towards each other. Since the static electric force between the
two will increase as the particles get closer together, the acceleration will also increase according to Newton's second law
(ΣF = ma).
Question 5
Explain why a parallel plate capacitor with a dielectric will have a smaller field strength between the plates than a similarly
designed air based parallel plate capacitor.
Correct Answer
When the dielectric is inserted, the field between the plates will cause the dielectric to polarize, which will cause weak
electric fields to form in the dielectric. These electric fields will be in the direction opposite the field between the two
capacitor plates. The superposition of fields will result in an overall weaker field.
Question 6
If two objects both have more of the negative type of charge than positive (referred to as a negative net charge)
Correct Answer
then the objects will repel each other.
Page 2 of 122
,Question 7
b. What causes steady state (direct) current? What causes alternating current?
Correct Answer
Steady, unchanging voltages such as those provided by batteries will create direct current. Fluctuating voltages will create
alternating current.
Question 8
Based on the plot of equipotentials shown in the example below, order the magnitude of the electric field strength at
points A, B, and C (from greatest to least).
Correct Answer
A>B>C
Page 3 of 122
, Question 9
A charged particle moving to the right enters a uniform magnetic field directed into the page. The charged particle
experiences a magnetic force. Which of the following is a true statement (disregard any gravitational effects)?
Correct Answer
The speed of the particle will remain the same.
Question 10
Two charged particles, each with a charge of +8.0 μC are at some position near each other. What is the distance between
the particles if the static electric force between them is 5.0 N?
Correct Answer
F = k q1 q2 / d^2
5 = 910^9 810^-6 8 * 10^-6 / d^2
d^2 = 0.576/5 = 0.1152
d= 0.34 m
Question 11
An electron moving to the right at a constant speed moves into an electric field. The electric field is to the left. Which of the
following correctly indicates how the field will affect the electron's motion?
Correct Answer
The electron will speed up.
Page 4 of 122
Question 1
A positive particle begins at a position near a negative plate and ends at a position near a positively charged plate. Which
statement is most accurate?
Correct Answer
Work is done on the particle so that the particle will end with more energy.
Question 2
Resistors of 10 Ω, 20 Ω, and 40 Ω are all connected in parallel to a 12 V battery. What is the current through the 20 Ω
resistor?
Correct Answer
V = IR
(12 V) = I (20 Ω)
I = 0.6 A
Question 3
Two charged parallel plates have a uniform field strength of 1200 N/C between them. If the separation distance between
the plates is 0.15 m, what is the potential difference between the plates?
Correct Answer
Page 1 of 122
,Question 4
Two charged particles have opposite net charges. They are placed near each other, and released from rest. Which of the
following statements best describes the motion of the particles?
Correct Answer
The particles will accelerate towards each other with an increasing acceleration.
Since the charges are opposite, they will attract, and move towards each other. Since the static electric force between the
two will increase as the particles get closer together, the acceleration will also increase according to Newton's second law
(ΣF = ma).
Question 5
Explain why a parallel plate capacitor with a dielectric will have a smaller field strength between the plates than a similarly
designed air based parallel plate capacitor.
Correct Answer
When the dielectric is inserted, the field between the plates will cause the dielectric to polarize, which will cause weak
electric fields to form in the dielectric. These electric fields will be in the direction opposite the field between the two
capacitor plates. The superposition of fields will result in an overall weaker field.
Question 6
If two objects both have more of the negative type of charge than positive (referred to as a negative net charge)
Correct Answer
then the objects will repel each other.
Page 2 of 122
,Question 7
b. What causes steady state (direct) current? What causes alternating current?
Correct Answer
Steady, unchanging voltages such as those provided by batteries will create direct current. Fluctuating voltages will create
alternating current.
Question 8
Based on the plot of equipotentials shown in the example below, order the magnitude of the electric field strength at
points A, B, and C (from greatest to least).
Correct Answer
A>B>C
Page 3 of 122
, Question 9
A charged particle moving to the right enters a uniform magnetic field directed into the page. The charged particle
experiences a magnetic force. Which of the following is a true statement (disregard any gravitational effects)?
Correct Answer
The speed of the particle will remain the same.
Question 10
Two charged particles, each with a charge of +8.0 μC are at some position near each other. What is the distance between
the particles if the static electric force between them is 5.0 N?
Correct Answer
F = k q1 q2 / d^2
5 = 910^9 810^-6 8 * 10^-6 / d^2
d^2 = 0.576/5 = 0.1152
d= 0.34 m
Question 11
An electron moving to the right at a constant speed moves into an electric field. The electric field is to the left. Which of the
following correctly indicates how the field will affect the electron's motion?
Correct Answer
The electron will speed up.
Page 4 of 122
