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WorksheetsElectric Forces - quiz
Total questions: 100
Worksheet time: 8mins
Doug rubs a piece of fur on a hard rubber rod, giving the rod a negative charge. What happens?
Protons are removed from the rod.
Electrons are added to the rod.
The fur is also charged negatively.
The fur is left neutral.
Negative ions added to the fur.
A repelling force must occur between two charged objects under which conditions?
charges are of unlike signs
charges are of like signs
charges are of equal magnitude
charges are of unequal magnitude
When a glass rod is rubbed with silk, which of the following statements best describes what happens?
electrons are removed from the rod
protons are removed from the silk
the silk is charged positively
the silk remains neutral
positive ions are removed from the silk
When charging two objects by rubbing them together:
neither may be a conductor.
they must be made of different material.
they will sometimes end up with both being positively charged.
the heat produced by friction is a necessary part of this process.
they must have different temperature.
Who was the first to determine the electron's charge?
Franklin D. Faraday
Coulomb E. Maxwell
Millikan
An uncharged conductor is supported by an insulating stand. I pass a positively charged rod near the left end of the conductor, but do not touch it. The right end of the conductor will be:
negative.
positive.
neutral.
attracted.
repulsed.
Of the following substances, which one contains the highest density of free electrons?
hard rubber
iron
amber
glass
silk
Which of the following best characterizes electrical conductors?
low mass density
high tensile strength
poor heat conductors
total electric charge is zero
Which of the following best characterizes electrical insulators?
charges on the surface don't move
high tensile strength
electric charges move freely
good heat conductors
low specific heat
If body P, with a positive charge, is placed in contact with body Q (initially uncharged), what will be the nature of the charge left on Q?
must be equal in magnitude to that on P
must be negative
must be positive
must be greater in magnitude than that on P
must be negative and less in magnitude than that on P
I wish to use a positively charged rod to charge a ball by induction. Which statement is correct?
The charge on the ball will be positive.
The ball must be a conductor.
The ball must be an insulator that is connected temporarily to the ground.
The ball is charged as the area of contact between the two increases.
The ball must be initially uncharged.
How can a charged object attract an uncharged object made of non-conducting material?
The uncharged object must somehow gain a like charge.
The uncharged object must somehow gain an unlike charge.
The charges in the uncharged object can become polarized.
Attraction of an insulator is not possible.
Attraction of an insulator is possible only by another insulator.
Two point charges are 4 cm apart. They are moved to a new separation of 2 cm. By what factor does the resulting mutual force between them change?
1/2
2
1/4
4
1
If the distance between two point charges is tripled, the mutual force between them will be changed by what factor?
9.0
3.0
0.33
1/9
6.0
If the size of the charge value is tripled for both of two point charges maintained at a constant separation, the mutual force between them will be changed by what factor?
1
3
6
9
The constant ke, which appears in Coulomb's law formula, is equivalent dimensionally to which of the following?
N·m/C
N/C
N·m2/C 2
N/C 2
N·C2/m 2
The beam of electrons that hits the screen of an oscilloscope is moved up and down by:
gravity.
a phosphorescent coating.
varying the electron's charge.
electrical charges on deflecting plates.
electrical repulsion between electrons.
Electric field is dimensionally equivalent to which of the following?
N·m/C
N/C
N·m2/C
N·m2/C 2
N/C
The electric field of a point charge has an inverse ___ behavior.
r1/2
r
r2
r3
r7/2
The number of electric field lines passing through a unit cross sectional area is indicative of:
field direction.
charge density.
field strength.
charge motion.
rate of energy transfer.
Relative distribution of charge density on the surface of a conducting solid depends on:
the shape of the conductor.
mass density of the conductor.
type of metal of which the conductor is made.
strength of the earth's gravitational field.
ambient temperature.
The electric field at the surface of a positively charged conductor has a direction characterized by which of the following?
tangent to the surface
perpendicular inward toward the charge
at a 45° angle to the surface
perpendicular outward and away from the charge
zero vector
The electric field associated with a uniformly charged hollow metallic sphere is the greatest at:
the center of the sphere.
the sphere's inner surface.
infinity.
the sphere's outer surface.
points inside the sphere.
At what point is the charge per unit area greatest on the surface of an irregularly shaped conducting solid?
where surface curves inward
where surface is flat
where curvature is least
where curvature is greatest
where surface curves outward
If a conductor is in electrostatic equilibrium near an electrical charge:
the total charge on the conductor must be zero.
the electric field inside the conductor must be zero.
any charges on the conductor must be uniformly distributed.
the sum of all forces between the conductor and the charge must be zero.
the total charge of the system must be zero.
An uncharged conducting spherical shell has a charge q carefully placed at its center through a small hole in the shell. The charge q does not touch the shell. What is the charge on the shell?
0
-q
q
-2q
2q
The combination of two separated point charges of opposite sign but equal magnitude is called an electric:
monopole.
dipole.
quadrupole.
magnanpole.
octapole.
The Millikan oil-drop experiment demonstrated that:
small oil drops fall slowly through the air.
light beams can be used to illuminate small oil droplets.
the electronic charge is quantized.
falling oil droplets reach terminal speed.
electric field can be used to control the falling of small oil drops.
A charge, +Q, is placed inside a balloon and the balloon is inflated. As the radius of the balloon r increases the number of field lines going through the surface of the balloon:
increases proportional to r^2.
increases proportional to r.
decreases as 1/r.
decreases as 1/r.
decreases as 1/r^2.
The unit of electrical potential, the volt, is dimensionally equivalent to:
J/C.
F·C.
B. J/C.
F/C.
The quantity of electrical potential, the volt, is dimensionally equivalent to:
force/charge
electric field/distance
electric field × distance
charge × distance
A free electron is in an electric field. With respect to the field, it experiences a force acting:
parallel.
anti-parallel (opposite in direction).
perpendicular.
along a constant potential line.
none of the above is correct in the general case.
In which case does an electric field do positive work on a charged particle?
A negative charge moves opposite to the direction of the electric field.
A positive charge is moved to a point of higher potential energy.
A positive charge completes one circular path around a stationary positive charge.
A positive charge completes one elliptical path around a stationary positive charge.
A negative charge moves in the direction of the electric field.
If the distance between two negative point charges is increased by a factor of three, the resultant potential energy is what factor times the initial potential energy?
3.0
1/9
1/3
9.0
1
Which of the following characteristics are held in common by both gravitational and electrostatic forces when dealing with either point masses or charges?
inverse square distance law applies
forces are conservative
potential energy is a function of distance of separation
charge and mass of isolated systems are conserved
all of the above choices are valid
At the point halfway between two spheres, one with charge +2 C and the other with –2 C, a proton is placed. What is not zero?
The electric field at the point
The electric potential at the point
Both the electric field and electric potential at the point
Neither the electric field nor the electric potential at the point
An electron in a TV picture tube is accelerated through a potential difference of 10 kV before it hits the screen. What is the kinetic energy of the electron in electron volts? (1 eV = 1.6 × 10⁻¹⁹ J)
1.0 × 10⁴ eV
1.6 × 10⁻¹⁵ eV
6.25 × 10²² eV
2.5 × 10²³ eV
1.6 × 10⁻²² eV
Electrons in an x-ray machine are accelerated from rest through a potential difference of 50,000 V. What is the kinetic energy of each of these electrons in eV?
50 eV
80 eV
330 eV
50 keV
80 keV
At which location will the electric field between the two parallel plates of a charged capacitor be the strongest in magnitude?
near the positive plate
near the negative plate
midway between the two plates at their ends
midway between the two plates nearest their center
anywhere between the two plates
The unit of capacitance, the farad, is dimensionally equivalent to which of the following?
V/C
V·C
J/V
C/V
V/J
Increasing the voltage across the two plates of a capacitor will produce what effect on the capacitor?
increase charge
decrease charge
increase capacitance
decrease capacitance
decrease charge and increase capacitance
A 0.25-μF capacitor is connected to a 400-V battery. Find the charge on the capacitor.
1.2 × 10⁻¹² C
1.0 × 10⁻⁴ C
0.020 C
0.010 C
0.010 C
If two parallel, conducting plates have equal positive charge, the electric field lines will:
leave one plate and go straight to the other plate.
leave both plates and go to infinity.
enter both plates from infinity.
be parallel to both plates.
none of the above.
A 20-μF capacitor is attached across a 1000-V power supply. What is the net charge on the capacitor?
10 mC
20 mC
40 mC
80 mC
none of the above
Increasing the separation of the two charged parallel plates of a capacitor, which are disconnected from a battery, will produce what effect on the capacitor?
increase charge
decrease charge
increase capacitance
decrease capacitance
decrease charge and increase capacitance
If three 4.0-μF capacitors are connected in parallel, what is the combined capacitance?
12 μF
0.75 μF
0.46 μF
5.5 μF
8.0 μF
Inserting a dielectric material between two charged parallel conducting plates, originally separated by air and disconnected from a battery, will produce what effect on the capacitor?
increase charge
increase voltage
increase capacitance
decrease capacitance
decrease voltage
The current in an electron beam in a cathode-ray tube is measured to be 70 μA. How many electrons hit the screen in 5.0 s? (e = 1.6 × 10⁻¹⁹ C)
A. 2.2 × 10¹¹ electrons
D. 8.8 × 10¹⁸ electrons
B. 8.8 × 10¹³ electrons
E. 2.2 × 10²⁰ electrons
C. 2.2 × 10¹⁵ electrons
A wire carries a steady current of 0.1 A over a period of 20 s. What total charge passes
1 C
2 C
3 C
4 C
If the current in a wire is tripled, what effect does this have on the electron drift velocity in the wire?
It stays the same.
It triples.
It decreases by a factor of three.
It increases by a factor of nine.
It decreases by a factor of nine.
The size of the electric current in an electrical conductor is a function of which of the following?
velocity of charge carriers
conductor cross sectional area
density of charge carriers
conductor length
All of the above choices are valid.
When an electric current exists within a conducting wire, which of the following statements describes the condition of any accompanying electric field?
must be zero
must be parallel to current flow
must be anti-parallel (opposite direction) to current flow
must be perpendicular to current flow
None of the above choices is valid.
Materials having resistance changes as voltage or current varies are called:
ohmic
inohmic
nonohmic
deohmic
ohlmless
You measure a 25.0-V potential difference across a 5.00-Ω resistor. What is the current flowing through it?
125 A
5.00 A
4.00 A
1.00 A
0.125 A
The unit of electric current, the ampere, is equivalent to which of the following?
V·Ω
V/Ω
Ω·m
V/s
Ω/V
The unit of electric resistance, the ohm, is equivalent to which of the following?
V/A
V·m
A/s
A/m
A/V
If a certain resistor obeys Ohm's law, its resistance will change:
The resistance will remain constant (Ohm's law states that resistance is constant for ohmic materials).
With increasing current through the resistor.
With increasing voltage across the resistor.
With the temperature of the resistor, regardless of Ohm's law.
A 60-W light bulb is in a socket supplied with 120 V. What is the current in the bulb?
0.50 A
2.0 A
60 A
7 200 A
10 000 A
The quantity volt is equivalent to which of the following?
J·m
J·C
C/Ω
J/C
C/J
The unit for rate of energy transformation, the watt, in an electric circuit is equivalent to which of the following?
V/s
A·Ω
V·A
V/Ω
A/V
If a 500-W heater carries a current of 4.00 A, what is the voltage across the ends of the heating element?
2 000 V
125 V
250 V
0.008 V
0.125 V
A light bulb has resistance of 240 Ω when operating at 120 V. Find the current in the light bulb.
2.0 A
1.0 A
0.50 A
0.20 A
0.30 A
Which is a unit of power?
kWh
W/s
A·Ω
J/s
J/kg
Which is not a force?
gravity
electrical force
voltage
friction
sliding resistance force
The two ends of a 3.0-Ω resistor are connected to a 9.0-V battery. What is the current through the resistor?
27 A
6.3 A
3.0 A
0.33 A
0.17 A
The two ends of a 3.0-Ω resistor are connected to a 9.0-V battery. What is the total power delivered by the battery to the circuit?
3.0 W
27 W
0.33 W
0.11 W
0.067 W
The basic function of an electromotive force in a circuit is to do which of the following?
Convert electrical energy into some other form.
Convert some other form of energy into electrical.
Both choices (a) and (b) are valid.
None of the above choices are valid.
Which voltage is not caused by a source of emf?
the voltage across a charged capacitor
the voltage across two copper-iron junctions at different temperatures
the voltage across the terminals of a dry cell battery
the voltage from an electric generator
None of the above choices is valid.
Three 8.0-Ω resistors are connected in series. What is their equivalent resistance?
24.0 Ω
8.0 Ω
0.38 Ω
0.13 Ω
0.075 Ω
Three resistors connected in series each carry currents labeled I1, I2 and I3. Which of the following expresses the value of the total current IT in the system made up of the three resistors in series?
IT = I1 + I2 + I3
IT = (1/I1 + 1/I2 + 1/I3)
IT = I1 = I2 = I3
IT = (1/I1 + 1/I2 + 1/I3)-1
IT = 3 I1 = 3 I2 = 3 I3
7. Three resistors connected in series have individual voltages labeled ΔV1, ΔV2 and _______.
ΔV3
ΔV4
ΔV5
ΔV6
Three resistors with values of R1, R2 and R3, respectively, are connected in series. Which of the following expresses the total resistance, RT, of the three resistors?
RT = R1 + R2 + R3
RT = (1 / R1 + 1 / R2 + 1 / R3)-1
RT = (1/ R1 + 1/ R2 + 1/ R3)
RT = R1 = R2 = R3
RT = 3 R1 = 3 R2 = 3 R3
Three resistors, with values of 2.0, 4.0 and 8.0 Ω, respectively, are connected in series. What is the overall resistance of this combination?
0.58 Ω
1.1 Ω
7.0 Ω
14.0 Ω
19.0 Ω
Three resistors, each with resistance R1, are in series in a circuit. They are replaced by one equivalent resistor, R. Comparing this resistor to the first resistor of the initial circuit, which of the following is true?
The current through R equals the current through R1.
The voltage across R equals the voltage across R1.
The power given off by R equals the power given off by R1.
R is less than R1.
R is equal to R1.
When a light bulb is turned on, its resistance increases until it reaches operating temperature. What happens to the current in the bulb as it is warming up?
It stays constant.
It increases.
It decreases.
It decreases at first and then increases.
It increases at first and then decreases.
Three resistors connected in parallel each carry currents labeled I1, I2 and I3. Which of the following expresses the value of the total current IT in the combined system?
IT = I1 + I2 + I3
IT = (1/ I1 + 1/ I2 + 1/ I3)-1
IT = (1/ I1 + 1/ I2 + 1/ I3)
IT = 3 I1 = 3 I2 = 3 I3
IT = I1 = I2 = I3
Three resistors connected in parallel have the individual voltages labeled ΔV1, ΔV2, ΔV3, respectively. Which of the following expresses the value of the total voltage ΔVT taken over the three resistors together?
ΔVT = ΔV1 + ΔV2 + ΔV3
ΔVT = (1/ ΔV1 + 1/ ΔV2 + 1/ ΔV3)
ΔVT = ΔV1 = ΔV2 = ΔV3
ΔVT = (1/ ΔV1 + 1/ ΔV2 + 1/ ΔV3)-1
ΔVT = 3 ΔV1 = 3 ΔV2 = 3 ΔV3
Three resistors with values R1, R2 and R3, respectively, are connected in parallel. Which of the following expresses the total resistance, RT, of the three resistors when connected in parallel?
RT = R1 + R2 + R3
RT = (1/ R1 + 1/ R2 + 1/ R3)
RT = R1 = R2 = R3
RT = (1/ R1 + 1/ R2 + 1/ R3)-1
RT = 3 R1 = 3 R2 = 3 R3
Three resistors, each with resistance R1, are in parallel in a circuit. They are replaced by one equivalent resistor, R. Compare this resistor to the first resistor of the initial circuit. Which of the following statements is true?
The current through R equals the current through R1.
The voltage across R equals the voltage across R1.
The power given off by R equals the power given off by R1.
R is greater than R1.
R is less than R1.
If R 1 < R 2 < R 3, and if these resistors are connected in parallel in a circuit, which one has the highest current?
R1
R2
R3
All have the same current.
The answer depends on the internal resistance of the battery.
Household circuits are wired in ___
series
parallel
both series and parallel
neither series nor parallel
In applications where electrical shocks may be more likely, such as around water in kitchens and bathrooms, special outlets called GFI's are used. What does GFI stand for?
get free instantly
gravity-free insulator
give fast interruption
ground-fault interrupter
guided fault isolation
19. Household 120-V outlets are made to accept three-pronged plugs. One of the prongs
is for grounding the appliance.
is for increasing voltage.
is for reducing current.
is for connecting to the neutral wire only.
What is the round third prong for?
It serves as a backup to the hot wire.
It lets the appliance run if the neutral wire breaks.
It connects the case of the appliance directly to ground for safety purposes.
It serves for direct current feed.
Nothing electrical, it is for mechanical sturdiness.
Electrical charges and magnetic poles have many similarities, but one difference is:
opposite magnetic poles repel.
one magnetic pole cannot create magnetic poles in other materials.
a magnetic pole cannot be isolated.
magnetic poles do not produce magnetic fields.
magnetic poles produce only alternating fields.
Which of the following is not a hard magnetic material?
iron
neodymium
cobalt
nickel
both b and c
Geophysicists today generally attribute the existence of the Earth's magnetic field to which of the following?
convection currents within the liquid interior
iron ore deposits in the crust
nickel-iron deposits in the crust
solar flares
iron-cobalt deposits in the crust
The term magnetic declination refers to which of the following?
angle between Earth's magnetic field and Earth's surface
Earth's magnetic field strength at the equator
tendency for Earth's field to reverse itself
angle between directions to true north and magnetic north
angle between Earth's magnetic field and Earth's rotational axis
The magnetic field of the Earth is believed responsible for which of the following?
deflection of both charged and uncharged cosmic rays
deflection of charged cosmic rays
ozone in the upper atmosphere
solar flares
deflection of uncharged cosmic rays
The magnetic pole of the Earth nearest the geographic North Pole corresponds to which of the following?
The magnetic south pole
The magnetic north pole
The geographic south pole
The geographic north pole
The force on a charged particle created by its motion in a magnetic field is maximum at what angle between the particle velocity and field?
zero
180°
90°
45°
135°
Assume that a uniform magnetic field is directed into this page. If an electron is released with an initial velocity directed from the bottom edge to the top edge of the page, which of the following describes the direction of the resultant force acting on the electron?
out of the page
to the right
to the left
into the page
from top edge to bottom edge of the page
A proton moves across the Earth's equator in a northeasterly direction. At this point the Earth's magnetic field has a direction due north and is parallel to the surface. What is the direction of the force acting on the proton at this instant?
toward the northwest
out of the Earth's surface
into the Earth's surface
toward the northeast
toward the southwest
Different units can be used to measure the same physical quantity, differing only by some multiplicative factor. The cgs unit for magnetic field, the gauss, is equal to ___ tesla.
10⁴
10⁻⁴
0.5
4π
These units do not measure the same physical quantity.
If a proton is released at the equator and falls toward the Earth under the influence of gravity, the magnetic force on the proton will be toward the:
north
south
east
west
A stationary positive charge +Q is located in a magnetic field B, which is directed toward the right as indicated. The direction of the magnetic force on Q is:
toward the right.
up.
toward the left.
There is no magnetic force.
There is a magnetic force on a particle. It is possible that the particle is:
uncharged.
stationary.
moving in the direction of the magnetic field.
Which of the following devices makes use of an electromagnet?
loudspeaker
galvanometer
gyrocompass
both A and B
none of the above
The direction of the force on a current carrying wire located in an external magnetic field is which of the following?
perpendicular to the current
perpendicular to the field
parallel to the wire
Both choices A and B are valid.
None of the above are valid.
A circular current loop is placed in an external magnetic field. How is the torque related to the radius of the loop?
directly proportional to radius
inversely proportional to radius
directly proportional to radius squared
inversely proportional to radius squared
directly proportional to square root of radius
