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SAMPLE: Test #5 Electricity & Magnetism (SPH 4U1)
Name:_________________
PART A Full Solution Problems
1. Three charges are placed at the corners of an equilateral triangle with sides of length 2.0m.
Calculate:
a)
b)
c)
The net force acting on sphere A. [4]
The electric field at the midpoint of the side between A and B [4]
The electric potential at the midpoint of the side between A and B. [1]
A
2. 0m
2.0 106 C
2. 0m
B
C
6
2.0 10 C
2.0 106 C
2. 0m
2. A proton with a charge of 1.60  10–19 C is shot from plate B toward plate A with a speed of 1.5  106 m/s.
(
d = 0.0030 m)
(a) What is the electric potential between the plates? [1]
(b) What will the speed of the proton be just before it hits plate A?[3]
3. An electron with an initial velocity of 2.00  106 m / s [horizontally] passes through two horizontal parallel
plates, as in the diagram below. The magnitude of the electric field between the plates is 150.N / C . The
plates are 5.0  10 2 m long.
(a) Calculate the vertical deflection (displacement) of the electron. [3]
(b) Calculate the electron’s final velocity (magnitude and direction) as it emerges from the plates. [3]
4. In a Millikan-type experiment, two horizontal parallel plates are 2.0 cm apart. A sphere of mass 2.0  10–13 kg
remains stationary when the potential difference between the plates is 400. V with the upper plate negative.
(a) Is the sphere positively or negatively charged? Explain. [1]
(b) Calculate the magnitude of charge on the sphere.[3]
(c) How much excess or deficit of electrons does the sphere have (round down)? [1]
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5. An electron accelerates from rest through an electric field and into a magnetic field as shown in the diagram
below. The plates have a potential difference of 85 V and the magnetic field has a magnitude of 0.75 T.
(Remember: me = 9.1  10–31 kg and e = 1.6  10–19 C.)
(a) Calculate the initial speed of the electron upon entering the magnetic field. [2]
(b) Calculate the magnitude and direction of the magnetic force on the electron. [2]
(c) Calculate the radius of the electron’s circular path. [2]
6. As the distance between two point charges increases, explain what happens to the electric potential energy of
the system when the two charges (i.e. does it increase or decrease and why);
a. have the same sign
b. have opposite signs.
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7. PART B Multiple Choice: Mark on your scantron the best choice and circle on your test paper.
____
1. The electrostatic force between two point charges is
. If the distance between the charges is tripled
but the size of the charges remains the same, the force between them will be
a.
d.
N
N
b.
e.
N
N
c.
N
____
2. Four charged spheres, A, D, P, and T are arranged as shown below. Sphere A has a charge of
sphere D has a charge of
____
____
C, sphere P has a charge of
C,
C, and sphere T has a charge of
C. Which two spheres exert the smallest force on each other?
a. A and D
d. P and D
b. A and T
e. P and T
c. A and P
3. The electric field 0.50 m from a small sphere with a positive charge of 7.2  10–5 C is
a. 2.6  106 N/C [inward]
d. 2.9  10–4 N/C [inward]
–4
b. 2.9  10 N/C [outward]
e. 2.6  106 N/C [outward]
c. 1.3  106 N/C [outward]
4. The magnitude of the electric field between the plates of a parallel plate capacitor is 3.5  104 N/C. If the
charge on each plate were to decrease by a factor of four, the magnitude of the electric field would
a. increase by a factor of four
d. decrease by a factor of four
b. increase by a factor of sixteen
e. not be affected
c. decrease by a factor of sixteen
____
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____
____
____
____
6. Two 2.0-kg spheres each carry a charge of 2.0 C. How does FE compare with Fg?
a. FE = Fg
b. Fg > FE
c. FE > Fg
d. If the charges on the spheres are the same, then Fg > FE, but if the charges are opposite
then FE > Fg.
e. FE and Fg cannot be compared without knowing the distance between the spheres..
7. In the electromagnet circuit below identify the polarity of the tops of the electromagnets.
a. Top left North, Top right North
d. Top left North, Top right South
b. Top left South, Top right North
e. Top left Neutral, Top right Neutral
c. Top left South, Top right South
8. The potential difference between two parallel plates is 1.7  104 V. To move a small charge from one plate to
another opposing the electric field requires 0.56 J of work. The magnitude of the charge is
a. 3.0  104 C
d. 3.3  10–5 C
b. 9.5  103 C
e. 4.8  10–15 C
–15
c. 1.5  10 C
9. A positively charged particle of mass 3.0  10–12 kg and charge +6.4  10–5 C is perpendicular to a 1.5-T
magnetic field. If the particle has a speed of 4.8  103 m/s, the acceleration of this particle is
a. 3.4  10–4 m/s2
d. 1.5  10–4 m/s2
–20
2
b. 2.6  10 m/s
e. 1.7  1019 m/s2
11
2
c. 1.5  10 m/s
____ 10. A conductor is located between the poles of a horseshoe magnet. Current flows in the direction indicated by
the arrow on the diagram.
In which direction will the conductor move?
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a. upward
b. left
c. downward
d. right
e. out of the page
Constants:
melectron  9.1 10 31 kg
m proton  1.67  10 27 kg
k  9.0  109 Nm 2 / C 2
qelectron  1.6  10 19 C
MULTIPLE CHOICE ANSWERS: DEEDCDDCC
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