Modified True/False
Indicate
whether the sentence or statement is true or false. If false, change the identified word or
phrase to make the sentence or statement true.
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1.
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If
electrons are removed from an object, it will be charged negatively.
_________________________
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2.
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A
negatively charged ebonite rod is brought near a neutral, metallic-coated pith ball. Some of the
electrons are repelled by the ebonite rod and move to the far side of the pith ball. This process is
called charging by induction. ___________________________________
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3.
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If a
negatively charged ebonite rod is brought close to the knob of a neutral electroscope and you touch
the electroscope, some electrons will leave the electroscope and travel through your hand to your
body. When you remove your hand the charge on the electroscope will be positive.
_________________________
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4.
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Coulomb’s law is extremely accurate under the conditions that the spheres are
small and that the spheres are also small compared to the distance between them.
______________________________
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5.
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When
the charge on both spheres is doubled, the electric force is increased by a factor of four.
_________________________
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6.
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If
q1 and q2 are opposite charges, they attract and the electric
potential is a negative value, as in the case of gravitational potential energy.
_________________________
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7.
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The
unit of electric potential is joules per volt. _________________________
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8.
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The
diagram below represents the electric potential near a negative charge. The electric potential
is large near the charge and decreases, approaching zero, as r increases.
_________________________
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9.
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According to the diagram below, for a negative charge, the electric potential is a
large negative value near the charge and increases, approaching zero, as r increases.
_________________________
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10.
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If a
charge moves one-quarter of the distance between two parallel plates, the charge will experience a
potential difference of  .
_________________________
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11.
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When
the net force on an oil drop in a Millikan apparatus is zero, the gravity downward cancels the
product of the mass and the electric field on the oil drop.
__________________________________________________
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12.
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The
elementary charge e, to four significant digits, is 1.602 ´
1023 C. _________________________
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13.
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In an
inkjet printer, the ink droplets acquire an electric charge by induction.
_________________________
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14.
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The
relative strength of the magnetic field is indicated by the spacing of adjacent field lines. The
farther apart the lines, the stronger the magnetic field.
______________________________
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15.
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The
magnitude of a magnetic field is determined by the magnitude of the turning action on a small test
compass aligned with the direction of the magnetic field.
_________________________
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16.
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The
north pole of a compass points toward the true north. _________________________
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17.
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Some
ferromagnetic materials are aluminum, nickel, calcium, and gadolinium.
______________________________
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18.
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When
a material has a permeability close to 1, it means that the magnitude of the magnetic field will
be close to that of a vacuum. _________________________
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19.
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In
two-dimensional diagrams of magnetic fields dots are drawn to represent field lines pointing
out of and perpendicular to the page. ______________________________
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20.
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The
motion of a charged particle does not influence the direction of gravitational or electric
forces. _________________________
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21.
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The
magnetic field around a straight conductor consists of field lines that are concentric circles. The
circles become more widely spaced as the distance from the conductor decreases.
_________________________
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22.
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Measurements of the magnetic field strength show that  . _________________________
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23.
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The
SI definition of the ampere is a magnetic one and depends on an understanding of the force between
two perpendicular current-carrying conductors. _________________________
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24.
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When
the current is constant in the primary coil of an induction apparatus, then a current is
induced in the secondary coil. _________________________
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25.
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A
larger current is produced when a magnet is plunged into a solenoid by using a stronger
magnet. _________________________
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Multiple Choice
Identify the
letter of the choice that best completes the statement or answers the question.
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26.
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A
piece of paper becomes electrically charged when a charged rod of plastic is placed close to it. This
is referred to as a. | charging by a
conductor | d. | charging by
contact | b. | charging by induction | e. | charging by electricity | c. | charging by an
insulator | | | | |
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27.
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To
charge an electroscope negatively by induction you need a. | a negatively
charged rod | d. | two objects of
opposite charges | b. | two objects of the same charge | e. | a positively charged rod and a ground | c. | a negatively
charged rod and a ground | | | | |
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28.
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When
a charge separation has been induced on an object, the charge on the object a. | is opposite to
the charge on the charging object | b. | is proportional to the size of the object being
charged | c. | is permanent | d. | is the same as
the charge on the charging object | e. | is inversely proportional to the size of the object being
charged | | |
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29.
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When
a negatively charged object makes contact with a neutral object, the negative charge is shared
between the two objects, and the objects both become negatively charged. This is an example
of a. | charging by
friction | d. | Coulomb’s
law | b. | charging by
contact | e. | charging by
induction | c. | induced charge separation | | | | |
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30.
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Which
subatomic particles are electrically charged? a. | neutrons only | d. | electrons and neutrons | b. | electrons and
protons | e. | protons
only | c. | protons and
neutrons | | | | |
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31.
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A
plastic rod is rubbed with silk. Both the plastic rod and the silk become charged. The charge on the
silk is due to a shortage of a. | electrons | d. | ions | b. | protons | e. | positrons | c. | neutrons | | | | |
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32.
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Four
charged spheres, A, D, P, and T are arranged as shown below. Sphere A has a charge of  C, sphere D has a charge of  C, sphere P has a charge of  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 | | | | |
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33.
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Which
of the following diagrams best illustrates the electric field in the area around two identical
charges?
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34.
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The
magnitude of the electric field between the plates of a parallel plate capacitor is 4.7 ´ 104
N/C. If the charge on each plate were to increase by a factor of three, the magnitude of the electric
field would a. | increase by a
factor of nine | d. | decrease by a
factor of three | b. | increase by a factor of three | e. | not be affected | c. | decrease by a
factor of nine | | | | |
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35.
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If
point charge +q was absent, the electric field at point B would be E. What is the electric
field between the two point charges, +q and –q, at point B which lies at the
midpoint between the two charges?
a. | 2E
[right] | d. |  [left] | b. | 0 | e. |  [right] | c. | 2E
[left] | | | | |
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36.
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The
magnitude of the electric field between the plates of a parallel plate capacitor is 4.7 ´ 104
N/C. If the plates were separated to a distance that is twice their original separation distance, the
magnitude of the electric field would a. | double | d. | decrease by a factor of sixteen | b. | be
halved | e. | not be
affected | c. | decrease by a factor of four | | | | |
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37.
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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.. | | |
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38.
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The
electric field intensity between two parallel plates is 300.0 N/C. The plates are connected to a
battery with an electric potential difference of 12.0 V. The separation of the plates
is a. | 25.0 m
| d. | 4.0 ´
10–7 m | b. | 3600.0 m | e. | 0.040 m | c. | 2.3 ´ 1011
m | | | | |
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39.
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The
number of electrons that must be removed from a sphere to give it a charge of 9.2 ´
10–5 C is a. | 1.7 ´ 1015 | d. | 8.3 ´ 105 | b. | 9.8 ´
1013 | e. | 1.7 ´
10–15 | c. | 5.8 ´ 1014 | | | | |
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40.
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A
small object has an excess of 4.7 ´ 1011 electrons. The electric potential at a distance of
0.200 m from the object would be a. | 2.7 ´ 106 V | d. | 3.4 ´ 103 N/C | b. | 3.4 ´ 103
V | e. | 2.6 ´ 106
N/C | c. | 2.1 ´ 1022
V | | | | |
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41.
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A
sphere of charge +q is in a fixed position. A smaller sphere +q is placed near the
larger sphere and released from rest. Which one of the following best describes its
motion? a. | decreasing
velocity and increasing acceleration | b. | decreasing velocity and constant
acceleration | c. | increasing velocity and decreasing
acceleration | d. | increasing velocity and increasing
acceleration | e. | decreasing velocity and decreasing
acceleration | | |
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42.
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The direction of the positively charged
particle’s velocity according to the diagram above must be a. | to the
left | b. | to the
right | c. | upward | d. | out of the page,
perpendicular to the page | e. | into the page, perpendicular to the
page | | |
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43.
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Which
of the following statements are true about a magnetic force and field?
I. A charged particle may travel
through a magnetic field without experiencing a magnetic force.
II. The magnetic field of a
current-carrying conductor points toward the conductor.
III. If you increase the magnetic
field, then you increase the kinetic energy of the charged particle travelling through the magnetic
field. a. | I
only | d. | II and III
only | b. | I and II
only | e. | III
only | c. | I and
III | | | | |
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44.
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Magnetic field strength is measured in a. | N | d. | kg·m/s2 | b. | N·C | e. | kg·m2/s2 | c. | kg/C·s | | | | |
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45.
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Magnetic force is equal to
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46.
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The
magnitude of the magnetic field 1.0 m from a long, straight conductor is 5.47 ´ 10–5
T. The current flowing through the wire must be a. | 2.7 ´ 102
A | d. | 1.8 ´ 104
A | b. | 4.3 ´
10–10 A | e. | 5.5 ´
10–5 A | c. | 1.1 ´ 10–11 A | | | | |
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47.
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What
is the magnetic field at point Y halfway between the two conductors in the diagram
below?
a. | zero | d. |  , into the page | b. |  , out of the
page | e. |  , into the page | c. |  , out of the page | | | | |
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48.
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What
will happen in the following diagram showing two current-carrying
conductors?
a. | The conductors
will attract one another. | b. | The conductors will both move upward. | c. | The conductors
will repel one another. | d. | The conductors will both move
downward. | e. | Nothing will happen. | | |
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49.
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A
permanent magnet is held still in the centre of a coil connected to a galvanometer. The galvanometer
needle will a. | steadily
increase | d. | steadily
decrease and then increase | b. | steadily decrease | e. | be steady and have a zero reading | c. | be steady and
have a nonzero value | | | | |
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50.
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In
the diagram below, a permanent magnet is pulled upward through a horizontal loop of
wire.
Which of the following describes the induced current as viewed from
above? a. | clockwise then
counterclockwise | d. | counterclockwise | b. | clockwise | e. | No current is induced. | c. | counterclockwise
then clockwise | | | | |
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Completion
Complete each sentence or
statement.
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51.
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The
law of ____________________ states that opposite charges attract one another, similar charges repel
one another, and charged objects attract some neutral objects.
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52.
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You
bring a negatively charged rod close to a neutral electroscope. You touch the electroscope with your
finger and some electrons move from the electroscope to your body. You take your finger away leaving
the electroscope with a positive charge. This is an example of
_________________________.
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53.
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The
______________________________ states that the total charge within an isolated system is
conserved.
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54.
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Electrophoresis is used in DNA fingerprinting. It separates molecules using
____________________.
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55.
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In
the region between two parallel plates the electric field is ____________________.
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56.
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The
value of potential energy per unit positive charge is referred to as the
_________________________.
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57.
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The
amount of work required per unit charge to move a positive charge from one point to another in the
presence of an electric field is referred to as the ______________________________.
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58.
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The
electric field direction is from the (+) plate to the (–) plate, in the direction of
____________________ potential.
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59.
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In
the Millikan experiment, the mass of any individual oil drop may be determined by measuring the
_________________________ with which it falls when the electric balancing force is
removed.
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60.
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All
subatomic particles have charges that are integral ____________________ of e.
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61.
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Opposite magnetic poles ____________________. Similar magnetic poles
___________________.
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62.
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The
symbol for a magnetic field is ____________________.
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63.
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_____________________________ is the angle between the magnetic north and the
geographic north that varies from position to position on the surface of Earth.
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64.
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______________________________ is the angle between Earth’s magnetic field at any
given point and the horizontal.
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65.
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Earth
has two major radiation belts, the ______________________________ approximately 25 500 km above the
surface of Earth and the ___________________________ approximately 12 500 km above the surface of
Earth.
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66.
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The
force of ____________________ is much weaker than ____________________ or ____________________
forces.
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67.
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When
a conductor is placed in a magnetic field, the angle between the conductor and the magnetic field
lines must be ____________________ to achieve maximum magnetic force.
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68.
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Complete the following equation:  .
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69.
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When
a magnet is plunged into a solenoid, the greater the current change, the ____________________ the
induced current.
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70.
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When
a magnet is plunged into a solenoid, the magnetic field is changing most when the loop is
____________________ to the field.
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Short Answer
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71.
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State
two ways that Coulomb’s law is similar to the Newton’s law of universal
gravitation.
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72.
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Two
identical spheres have a negative charge q, and are separated by a centre-centre distance
r. State the effect the following changes will have on the electric force F exerted by
each sphere:
(a) the distance
between the two spheres increases to  r
(b) the charge
on each sphere becomes 2q
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73.
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Briefly explain one feature of a coaxial cable that shields the electric current being
transmitted from stray electric fields.
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74.
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Explain briefly the feature of a lightning rod that makes it a better acceptor of
lightning than a rooftop.
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75.
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Describe briefly how Robert Millikan was able to calculate the total electric charge
on an oil drop.
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76.
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Draw
a current-carrying conductor showing its magnetic field and the direction of current
flow.
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77.
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Draw
a loop showing the magnetic field and the current flow.
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78.
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Draw
a solenoid showing the magnetic field and current flow.
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79.
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Explain, using the domain theory, why a needle is magnetized when it is rubbed in one
direction with a strong magnet.
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80.
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Explain, using the domain theory, why the beams in a building are often
magnetized.
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81.
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State
the right-hand rule for determining the direction of magnetic force for a positive charge moving
through a magnetic field.
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82.
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In
the diagram above, a positive particle is moving in a uniform circular path in a magnetic field. On
the diagram, indicate the direction of the velocity with arrows.
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83.
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In
the diagram above, a negative particle is moving in a uniform circular path in a magnetic field. On
the diagram, indicate the direction of the velocity with arrows.
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84.
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J.J.
Thomson’s ideas led to the development of another important device.
(a) What was the
device?
(b) What does the device do and how does it achieve
this?
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85.
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The
discoveries in electric and magnetic fields have led to other scientific research. List two other
areas of research that link these two fields.
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86.
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State
Ampere’s law.
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87.
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Define one coulomb.
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88.
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State
Lenz’s law.
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89.
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Why
is Lenz’s law consistent with the law of conservation of energy?
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90.
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Even
though the cooktop on an induction stove is cool, you would not place your hand on it if you were
wearing a ring made of metal. Why?
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Problem
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91.
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Three
identical point charges A, B, and C are located as shown on the diagram. A exerts force F on
B. An equal force F is exerted by C on B ( ). What is the
net force on B?
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92.
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Two
charged spheres are 2.00 m apart. One sphere has a charge of  and the other sphere has a charge of  . Assuming
k =  , what is the electric force between the two
spheres?
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93.
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The
electrostatic force between two point charges is  . If the
distance between them is doubled, the charge of one of the points doubles and the charge of the other
point triples. What will be the force between them?
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94.
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Calculate the electric field 1.0 m from a small sphere with a positive charge of 3.2
´
10–3 C.
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95.
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Two
charges, one of charge +2.5 ´ 10–5 C and the other of charge –3.7 ´
10–7 C, are 25.0 cm apart. The positive charge is to the left of the negative charge.
(a) Draw a diagram showing the point charges and label a point Y that is 10.0 cm away
from the negative charge, on the line connecting the charge. (Field lines do not need to be
drawn.)
(b) Calculate the electric field at point Y.
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96.
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In a
Millikan-type experiment, two horizontal parallel plates are 1.0 cm apart. A sphere of mass 2.2
´
10–13 kg remains stationary when the potential difference between the plates is 350 V
with the upper plate negative.
(a) Is the
sphere positively or negatively charged? Explain.
(b) Calculate the magnitude of charge on the
sphere.
(c) How much
excess or deficit of electrons does the sphere have?
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97.
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Calculate 1.92 ´ 10–18 C as a multiple of the elementary
charge.
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98.
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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.
(b) Calculate the magnitude and direction of the magnetic force on the
electron.
(c) Calculate the radius of the electron’s circular
path.
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99.
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(a)
Calculate the speed of a proton with mass 1.67 ´ 10–27 kg, travelling a circular path through a
radius of 8.0 cm, in a plane perpendicular to a 4.2-T magnetic field.
(b) What
potential difference would be required to accelerate the proton from rest in a vacuum to this
speed?
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100.
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At
what distance from a straight conductor, carrying a current of 15.0 A, is the magnitude of the
magnetic field 9.4 ´ 10–6 T?
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