Honors Physics
Spring, 2017
Electrostatics Test Review
Name:
Mr. Leonard
Instructions: Complete the following worksheet.
SHOW ALL OF YOUR WORK ON A SEPARATE SHEET OF PAPER.
1. Determine whether each statement is True or False. If the statement is false, correct the statement so
that it is true.
(a)
Oppositely charge particles experience an attractive Coulomb Force.
(b)
Charge can be created by voltage sources such as a battery.
(c)
Electric fields are useful when describing the Coulomb Force, but are not necessary for a
complete description of electro-magnetic interactions.
(d)
The electric field is a vector field. Which means there is a vector, corresponding to the
strength and direction of the electric field, at every point in space.
(e)
The electric field inside a conductor is always zero.
(f)
Closely spaced electric field lines indicate a strong electric field.
Honors Physics/Electrostatics Test Review
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2. Use an arrow to indicate the direction of the net force acting on the positive charge +q.
+q
(a)
(b)
+Q
+Q
−Q
+q
+Q
+q
(c)
+Q
3. Sketch the electric field lines for the two charges shown below.
+Q
Honors Physics/Electrostatics Test Review
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Name:
4. To measure the charge on an object, the object is placed 3.0 cm away from a plastic ball which has
N
a charge of 1.5 µC. The ball is attached to a spring which has a spring constant of 250
. The
m
experimenter finds that the spring is compressed by 12 cm. What was the charge on the object?
Be careful when working through this problem. There are two variables which we denote with the letter
’k’: the spring constant, and Coulomb’s Constant. You may want to invent a new notation for this
problem, such as using a cursive k for the spring constant and a manuscript k for Coulomb’s constant.
∆x = 12 cm
k = 250 N/C
1.5 µC
q=?
3.0 cm
(a) What is the sign of the charge on the object?
(b) What is the charge on the object?
5. The experimenter attempts to improve the measuring device by placing the charged object in a uniform
N
electric field. Once again, a charged object is attached to a spring with spring constant of 250
.
m
N
However, this time, a 4.0 (105 )
uniform electric field is applied to the charged object as shown in the
C
figure below. The electric field stretches the spring by 1 cm.
~
E
∆x = 1 cm
k = 250 N/m
q=?
(a) What is the sign of the charge on the object?
(b) What is the charge on the object attached to the spring?
6. Two charges are shown in the figure below.
+3.0 µC
−2.0 µC
1.0 m
(a) Calculate the location of the point between the two charges where the voltage is zero.
(b) The voltage is also zero for some point outside the two charges. Is this point to the left or right of
the two charges shown in the figure? Explain your reasoning.
(c) Calculate the location of the point outside the two charges where the voltage is zero.
Honors Physics/Electrostatics Test Review
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7. Two 4.5 µC charges are separated by 10 cm and 15 cm as shown in the figure below.
10 cm
A
+4.5 µC
15 cm
+4.5 µC
(a) Calculate the magnitude and direction of the electric field at point A.
(b) Calculate the voltage at point A.
8. Two 3.0 µC point charges are held in place 2.0 cm apart. Each charge has a mass of 2.0 grams. One of
the charges is released, while the other charge remains held in place. How fast is the charge traveling
when the charged particles are 4.0 cm apart?
9. A 15 gram, 10.0 µC point charge, is accelerated across a 25 kV potential difference (so that ∆V = −25
kV). How fast is the particle moving, assuming that it started from rest?
Honors Physics/Electrostatics Test Review
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Solutions to Electrostatics Test Review
1.
1.
1.
1.
1.
1.
4.
(a) True.
(b) False.
(c) False.
(d) True.
(e) True.
(f) True.
(a) positive.
4. (b) q = 2.0 µC
5. (a) Positive.
5. (b) q = 6.25 µC
6. (a) x = 0.6 m from the +3.0 µC charge.
6. (b) Right.
6. (c) x = 2.0 m
~ = 4.43 (106 )
7. (a) |E|
N
θ = 24.0◦ counter-clockwise from the +x-axis.
C
7. (b) V = 6.74 (105 ) V
m
s
m
9. vf = 5.77
s
8. vf = 63.6
SOLUTIONS