Curriculum
Course: American System Physics
time left:
:
:
Login

Curriculum

American System Physics

A Physics Toolkit

0/9

Representing Motion

0/9

Accelerated Motion

0/9

Forces in One Dimension

0/9

Displacement and Force in Two Dimensions

0/9

Motion in Two Dimensions

0/9

Gravitation

0/9

Rotational Motion

0/9

Momentum and Its Conservation

0/9

Energy and Its Conservation

0/9

Thermal Energy

0/9

States of Matter

0/9

Vibrations and Waves

0/9

Sound

0/9

Fundamentals of Light

0/9

Reflection and Refraction

0/9

Interference and Diffraction

0/9

Electrostatics

0/9

Electric Current and Circuits

0/9

Magnetic Fields

0/9

Electromagnetic Induction and Electromagnetism

0/9

Quantum Theory and the Atom

0/9

Solid-State Electronics

0/9

Nuclear and Particle Physics

0/9
Quiz

18.2 Electric Force and Coulomb’s Law – Quiz

Submit quiz
Once you submit, you will no longer be able to change your answers. Are you sure you want to submit the quiz?
Cancel Submit

Electric Force and Coulomb’s Law American Physics quiz: free practice for American System Physics. Work through this Electric Force and Coulomb’s Law American Physics quiz and get instant feedback on every answer. If you get stuck, review the 18.2 Electric Force and Coulomb’s Law — Notes lesson. More practice: American System Physics — all units. Syllabus: OpenStax free science textbooks.

  • Questions count: 50
  • Passing grade: A-
  • Time limit:
Start Quiz
1.
Two point charges of +4.0 μC and +6.0 μC are 0.30 m apart. What is the size of the force between them?
2.4 N
0.72 N
2.4 × 10¹² N
24 N
2.
A +2.0 nC charge is 5.0 cm from a −5.0 nC charge. What is the size of the force?
3.6 × 10⁻⁹ N
3.6 × 10⁻⁵ N
1.8 × 10⁻⁶ N
36 N
3.
Two equal charges of 3.0 μC repel with a force of 0.90 N. How far apart are they?
0.090 m
0.90 m
0.30 m
0.60 m
4.
Two identical charges 0.20 m apart repel with a force of 0.50 N. What is the size of each charge?
2.2 × 10⁻⁷ C
2.2 × 10⁻¹² C
1.5 × 10⁻⁵ C
1.5 × 10⁻⁶ C
5.
Estimate the electrical attraction holding the electron in a hydrogen atom, given an electron–proton distance of 5.3 × 10⁻¹¹ m.
8.2 × 10⁻⁸ N
4.3 × 10⁻¹⁸ N
8.2 × 10⁻¹⁸ N
819 N
6.
The force between two charges is 16 N. What is the force when the separation is doubled?
8.0 N
32 N
4.0 N
64 N
7.
The force between two charges is 5.0 N. Both charges are doubled and the separation is unchanged. What is the new force?
10 N
5.0 N
2.5 N
20 N
8.
Starting from an 18 N attraction, one charge is made three times bigger while the gap is also made three times bigger. What force results?
6.0 N
18 N
2.0 N
54 N
9.
Two charges repel with 9.0 N. The separation is halved and one charge is halved. What is the new force?
9.0 N
18 N
36 N
4.5 N
10.
The diagram shows three point charges on a line. What is the size of the net force on charge B?
Dr Dabour Hub Academy - figure 1
7.2 N
4.8 N
6.0 N
1.2 N
11.
Charge C pulls or pushes charge B. Looking at the signs shown, which way does C push or pull B?
Dr Dabour Hub Academy - figure 2
Towards A (the −x direction)
Towards C (the +x direction)
Perpendicular to the line
There is no force
12.
The diagram shows charges P (+4.0 μC) at x = 0 and Q (+1.0 μC) at x = 0.60 m. Where between them would a small positive test charge feel zero net force?
Dr Dabour Hub Academy - figure 3
x = 0.30 m
x = 0.20 m
x = 0.40 m
x = 0.48 m
13.
Charge C in the diagram is attracted by A and by B. What is the size of the net force on C?
Dr Dabour Hub Academy - figure 4
0.37 N
0.031 N
0.20 N
0.26 N
14.
For the charges in the diagram, which method correctly finds the net force on C?
Dr Dabour Hub Academy - figure 5
Find each force separately, then add them as vectors using Pythagoras because they are perpendicular
Add the two force sizes directly
Add the charges first and use the 0.5 m diagonal
Subtract the smaller force from the larger
15.
The graph shows force against separation for two charges. By what factor does the force change from r = 0.10 m to r = 0.20 m?
Dr Dabour Hub Academy - figure 6
It falls to one half
It falls to one quarter
It doubles
It falls to one eighth
16.
A student measures F for several separations r (graph shows F against 1/r²). What does the straight line through the origin confirm?
Dr Dabour Hub Academy - figure 7
F is proportional to r
F is inversely proportional to r
F is inversely proportional to r²
F does not depend on r
17.
In the F against 1/r² graph for two equal charges q, the gradient is 9.0 × 10⁻³ N m². What is q?
Dr Dabour Hub Academy - figure 8
1.0 × 10⁻¹² C
9.0 × 10⁻⁶ C
1.0 × 10⁻³ C
1.0 × 10⁻⁶ C
18.
Which conclusion do the torsion-balance results in the table support?
F × r² is constant, so F ∝ 1/r²
F × r is constant, so F ∝ 1/r
F is proportional to r
F is independent of r
19.
In the torsion-balance experiment in the table, which variable must be kept constant?
The separation r
The force F
The charges on the two spheres
The angle of twist
20.
The charges in the torsion-balance experiment slowly leak away during the investigation. What effect does this have?
No effect, because charge is conserved
Forces become larger over time
It only affects the units
Later forces are too small, a systematic error that makes F fall faster than 1/r²
21.
Given the table, why does gravity dominate on astronomical scales?
G is larger than k
Electric forces only act on electrons
Large bodies are almost exactly neutral, but mass is always positive and adds up
Gravity is not an inverse-square law
22.
Which values correctly complete the table, in order?
2F; F/3
4F; F/3
8F; F/6
4F; F/9
23.
Which pairs in the table experience the same size of force?
W, X and Z
W and Y only
X and Y only
All four
24.
A charged pith ball of mass 2.0 g hangs at rest with its thread at 10.0° to the vertical because of a horizontal electric force. What is the electric force? (g = 9.8 N/kg)
4.4 × 10⁻³ N
0.020 N
3.5 × 10⁻³ N
3.5 N
25.
Two small spheres, each with charge +2.0 μC, are released 5.0 cm apart. One has mass 10 g. What is its initial acceleration?
1.4 m/s²
14 m/s²
1.4 × 10⁵ m/s²
1438 m/s²
26.
A +8 μC charge and a +2 μC charge of equal mass are released near each other. Which statement is correct?
They feel equal forces and have equal accelerations
The 2 μC charge feels 4 times the force
The 8 μC charge accelerates 4 times faster
The 8 μC charge feels no force
27.
What is the SI unit of the Coulomb constant k?
N m²/C²
C²/(N m²)
N/C
J/C
28.
Which instrument did Coulomb use to measure electric forces?
A gold-leaf electroscope
A torsion balance
A spectrometer
An ammeter
29.
A student calculates a force of 3.6 × 10¹² N between two 2.0 μC charges 0.10 m apart. What mistake was made?
r was not squared
k was divided instead of multiplied
The microcoulombs were not converted to coulombs
The charges should be added
30.
A student writes "F is inversely proportional to the distance." How should this be corrected?
F is proportional to the distance
F is inversely proportional to the charge
F is proportional to the distance squared
F is inversely proportional to the square of the distance
31.
Which method would best test how the Coulomb force depends on the charge?
Keep r fixed, share charge between identical spheres to halve it repeatedly, and measure F each time
Change r and q at the same time
Use spheres of different sizes at different distances
Measure the mass of the spheres
32.
Why can microcoulomb charges a few centimetres apart produce forces of several newtons?
Because charges are always large
Because k is extremely large (about 9 × 10⁹ N m²/C²)
Because r is squared in the numerator
Because gravity adds to the force
33.
A +q charge is placed midway between two identical +Q charges. What is the net force on it?
Twice the force from one charge
Four times the force from one charge
Zero
Towards the nearer charge
34.
If the distance between two point charges is tripled, the force becomes _____ of the original.
one third
three times
one ninth
nine times
35.
The missing "Direction" entry for the electric force in the table is _____.
attract or repel
attract only
repel only
neither
36.
The electric force between two point charges is inversely proportional to the _____ of the distance between them.
cube
square root
reciprocal
square
37.
Two forces that two charges exert on each other form an _____ pair.
action–reaction
equilibrium
induction
polarization
38.
The permittivity of free space has the value ε₀ = _____ C²/(N m²).
8.99 × 10⁹
8.85 × 10⁻¹²
6.67 × 10⁻¹¹
1.60 × 10⁻¹⁹
39.
For two protons, the electric force is about 10³⁶ times larger than the gravitational force at any separation. True or false?
False, gravity is stronger for protons
True
False, the ratio depends on separation
True only when they are very close
40.
Moving two charges to half their original separation makes the force between them four times larger. True or false?
False, it becomes twice as large
False, it becomes half as large
True only for unlike charges
True
41.
Using the table, the force at r = 30.0 cm would be 2.0 mN. True or false?
False, it would be 3.0 mN
True
False, it would be 6.0 mN
True only if the charges doubled
42.
The table shows both forces follow the same distance dependence. True or false?
False, gravity is inverse, electric is inverse square
True
False, electric force is independent of distance
True only in a vacuum
43.
In the table, pair X experiences an attractive force. True or false?
False, it is repulsive
True
False, there is no force
True only if r is doubled
44.
The larger of two charges experiences the larger electric force. True or false?
True, force depends on the charge
False, because both feel equal and opposite forces
True only if the charges are unlike
False, because the smaller charge feels more
45.
In Coulomb's law, r is measured between the surfaces of two charged spheres. True or false?
True, it is always surface to surface
True only for small spheres
False, because r is measured between centres
False, it is measured from one surface to the far surface
46.
A negative product q₁q₂ in Coulomb's law means the force is attractive. True or false?
False, it means the force is smaller
False, it means repulsion
True only in water
True
47.
Electric forces are responsible for contact forces such as friction and tension at the atomic level. True or false?
True
False, those are gravitational
False, contact forces have no cause
True only for metals
48.
The Coulomb constant k is equal to 1/(4πε₀). True or false?
False, it equals 4πε₀
True
False, it equals ε₀
True only for air
49.
Doubling both the charges and the separation leaves the Coulomb force unchanged. True or false?
False, the force doubles
False, the force quarters
True
True only for unlike charges
50.
Coulomb's law applies to point charges and to uniformly charged spheres. True or false?
False, only to electrons
False, only to flat plates
True only if the spheres touch
True
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 14
  • 15
  • 16
  • 17
  • 18
  • 19
  • 20
  • 21
  • 22
  • 23
  • 24
  • 25
  • 26
  • 27
  • 28
  • 29
  • 30
  • 31
  • 32
  • 33
  • 34
  • 35
  • 36
  • 37
  • 38
  • 39
  • 40
  • 41
  • 42
  • 43
  • 44
  • 45
  • 46
  • 47
  • 48
  • 49
  • 50
Part of Electrostatics — see every lesson and quiz in this unit.
Accepted payment methods