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Quizzes > High School Quizzes > Science

Coulombs Law Practice Quiz

Master Coulombic Attraction Concepts with Confidence

Difficulty: Moderate
Grade: Grade 11
Study OutcomesCheat Sheet
Colorful paper art promoting the Coulomb Charge Challenge physics quiz for students.

Which statement best describes Coulomb's Law?
It describes the gravitational attraction between masses.
It states that the electrostatic force between two point charges is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.
It explains the magnetic force between current-carrying wires.
It states that the force does not depend on the distance between charges.
Coulomb's Law expresses how the electrostatic force between two point charges depends on the magnitude of the charges and the distance between them. The correct formula reflects a direct proportionality to the product of the charges and an inverse square relationship with distance, unlike the other options which refer to different forces or incorrect dependencies.
What is the approximate value of Coulomb's constant (k) in free space?
8.99 Ć - 10^9 NĀ·mĀ²/CĀ²
6.67 Ć - 10^-11 NĀ·mĀ²/CĀ²
9.81 m/sĀ²
3.00 Ć - 10^8 m/s
Coulomb's constant, k, is approximately 8.99 Ć - 10^9 NĀ·mĀ²/CĀ² in free space. The other values are associated with the gravitational constant, the speed of light, and the acceleration due to gravity, respectively.
How does doubling the distance between two point charges affect the magnitude of the electrostatic force?
It decreases the force by a factor of 4.
It increases the force by a factor of 2.
It remains unchanged.
It decreases the force by a factor of 2.
According to Coulomb's Law, the force is inversely proportional to the square of the distance between the charges. Doubling the distance results in the force being reduced by a factor of 2Ā², which is 4.
What kind of interaction occurs between two like charges?
They attract each other.
They generate a magnetic field.
They combine to cancel out.
They repel each other.
Like charges repel each other as a fundamental property of electrostatics expressed by Coulomb's Law. This repulsion results from the similar nature of their charges, whereas attraction occurs only between opposite charges.
What is the nature of the force between two charges of opposite signs?
They attract each other.
They create a gravitational effect.
No force acts between them.
They repel each other.
Opposite charges attract each other, which is a key principle in electrostatics. This attractive force is described by Coulomb's Law and contrasts with the repulsive interaction between like charges.
Which of the following formulas correctly represents Coulomb's Law for the force between two charges?
F = k * |q1 - q2| / rĀ²
F = k * |q1 * q2| / rĀ²
F = k * (q1 + q2) / rĀ²
F = k * |q1 * q2| * r
The correct expression for Coulomb's Law is F = k * |q1 * q2| / rĀ², where the absolute value ensures that the magnitude of the force is positive. The other options incorrectly combine or manipulate the charges and distance.
If the distance between two charges is tripled, by what factor does the electrostatic force change?
The force is reduced by a factor of 9.
The force is increased by a factor of 9.
The force is reduced by a factor of 3.
The force is increased by a factor of 3.
Since Coulomb's Law is inversely proportional to the square of the distance, tripling the distance reduces the force by a factor of 3Ā², which is 9. This clearly demonstrates the inverse square dependency.
Which physical quantity does NOT influence the magnitude of the electrostatic force between two charges?
Distance
Mass
Coulomb's constant
Charge
Coulomb's Law depends on the magnitude of the charges, the distance between them, and Coulomb's constant. Mass does not affect the calculation of the electrostatic force between charges, making it the correct answer.
What are the standard SI units for electric charge?
Newtons (N)
Watts (W)
Coulombs (C)
Joules (J)
The SI unit for electric charge is the coulomb, abbreviated as C. The other units represent force, energy, and power, which are not applicable for measuring charge.
In Coulomb's Law, the distance (r) used in calculations is measured from:
Any arbitrary point between the charges.
The edges of the charges.
The centers of the charges.
The surfaces of the charges.
For point charges or spherically symmetric charge distributions, the distance is measured between their centers. This approach ensures the correct application of Coulomb's Law in calculating the force.
How does the medium between two charges affect the electrostatic force compared to a vacuum?
The force becomes zero in a medium.
The force is reduced due to the medium's dielectric constant.
The force increases in any medium.
The force remains the same regardless of the medium.
When charges are placed in a medium, the electrostatic force is typically reduced by the medium's dielectric constant. This reduction occurs because the medium partially counteracts the electric field, lowering the force compared to that in a vacuum.
Coulomb's Law is often compared to which astronomical law?
Hooke's Law
Newton's Law of Universal Gravitation
Ohm's Law
Kepler's Laws of Planetary Motion
Both Coulomb's Law and Newton's Law of Universal Gravitation involve an inverse square relationship with distance, making them analogous in form. This similarity is frequently used to illustrate fundamental force interactions in physics.
If the magnitude of one of two interacting charges is doubled while the other remains constant, the electrostatic force will:
Be doubled.
Be quadrupled.
Be halved.
Remain unchanged.
Doubling one charge directly doubles the product of the charges in Coulomb's Law, which in turn doubles the force. This illustrates the direct proportionality between the magnitude of the charges and the force between them.
Why does Coulomb's Law use the absolute value of the product of the charges in its formula?
To account for the vector direction of the force.
To indicate that only positive charges interact.
To simplify the calculation by disregarding negative values.
To ensure the calculated force always has a positive magnitude.
The use of the absolute value in Coulomb's Law ensures that the force magnitude is always a positive number, with the direction of the force being determined separately by the sign of the charges. This method avoids confusion between magnitude and vector direction in force calculations.
Which of the following correctly describes the electric field due to a point charge?
It is strongest at infinity.
It circulates around the charge.
It radiates outward from a positive charge and inward toward a negative charge.
It radiates inward for both positive and negative charges.
The electric field around a point charge emanates outward from a positive charge and converges inward toward a negative charge. This behavior reflects the fundamental principle of field lines indicating the direction of the force that a positive test charge would experience.
Calculate the magnitude of the electrostatic force between q1 = +5Ć - 10^-6 C and q2 = -10Ć - 10^-6 C separated by 0.2 m (Use k = 9Ć - 10^9 NĀ·mĀ²/CĀ²).
22.5 N
0.45 N
11.25 N
2.25 N
Using Coulomb's Law, F = k * |q1 * q2| / rĀ² yields F = 9Ć - 10^9 * |5Ć - 10^-6 * (-10Ć - 10^-6)| / (0.2)Ā² = 9Ć - 10^9 * 5Ć - 10^-11 / 0.04, which calculates to 11.25 N. The alternate answers result from common computational errors or misapplication of the formula.
A molecule in a dielectric medium experiences an electrostatic force that is 60% of what it would be in a vacuum. What is the approximate dielectric constant of the medium?
0.67
0.60
1.33
1.67
In a medium, the force is reduced by the dielectric constant (Īŗ) according to F_medium = F_vacuum/Īŗ. Given that F_medium is 60% of F_vacuum, Īŗ is approximately 1/0.60, which equals about 1.67. This reflects the inverse relationship between the dielectric constant and the electrostatic force.
How does the direction of the electrostatic force change when one charge in a pair is replaced by a charge of opposite sign?
The force direction remains the same.
The magnitude of the force becomes zero.
The force changes from repulsive to attractive, reversing its direction.
The force direction becomes perpendicular to the line joining the charges.
Replacing one charge with a charge of opposite sign changes the interaction from repulsive to attractive. This reversal in interaction causes the force to act in the opposite direction compared to the original configuration, clearly illustrating the role of charge sign in determining force direction.
Which modification is necessary in Coulomb's Law to account for the presence of a material medium?
Replace k with k times the medium's relative permeability.
Replace k with 1/(4Ļ€Īµ) where Īµ = Īµ0 * Īµr.
Multiply k by the medium's dielectric constant.
Add the medium's conductivity to the formula.
In a medium, Coulomb's Law is modified by replacing the constant k with 1/(4Ļ€Īµ), where Īµ is the permittivity of the medium given by Īµ0 multiplied by the relative permittivity (dielectric constant) Īµr. This adjustment accounts for the effect of the medium on the electrostatic interactions.
When analyzing the net electrostatic force on a charge due to multiple other charges, which method is most effective?
Averaging the forces without considering direction.
Considering only the largest force and ignoring the rest.
Using vector addition by decomposing each force into its components.
Adding the magnitudes of the forces directly.
The most effective strategy is to decompose each force into its horizontal and vertical components, then use vector addition to sum these components. This method accurately captures both magnitude and direction, which is essential for determining the net force in multi-charge systems.
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Study Outcomes

  1. Understand the principles of Coulomb's Law and its mathematical framework.
  2. Analyze the relationship between electrostatic force, charge magnitude, and distance separation.
  3. Apply Coulomb's Law to solve problems involving static electric charges.
  4. Calculate the force between point charges in various practical scenarios.
  5. Evaluate how changes in charge and distance affect the strength of electrostatic force.

Coulomb's Law & Attraction Worksheet Cheat Sheet

  1. Understand Coulomb's Law - Coulomb's Law measures the electrostatic force between two point charges, growing stronger with larger charges and weakening quickly as distance increases squared. Picture charges like super sticky friends - the closer they are, the stronger the pull, and vice versa! Physics Classroom
  2. Use the formula F = kĀ·(qā‚Ā·qā‚‚)/rĀ² - This famous equation calculates the force (F) based on the product of the charges (qā‚ and qā‚‚) divided by the square of their separation (r), with kā‰ˆ9.0Ɨ10ā¹ NĀ·mĀ²/CĀ². Try tweaking numbers: doubling r makes the force drop by four, a neat physics magic trick! Physics Classroom
  3. Like charges repel, opposites attract - Remember that two positive charges push each other away, while a positive and a negative charge pull towards each other. The force always acts along the line connecting them, so draw arrows carefully to track the direction! Physics Classroom
  4. Limit to point charges or spherical distributions - Coulomb's Law is most accurate for tiny point charges or perfectly spherical charge distributions where you can treat all charge as concentrated at a center. Extended shapes or moving charges need more advanced methods like integration or full Maxwell's equations. Wikipedia
  5. Practice superposition with multiple charges - When more than two charges are present, calculate each pair's force vector and add them up to find the net force. Drawing freeā€‘body diagrams and breaking forces into components will keep your calculations neat and errorā€‘free. Physics.info
  6. Master the electric field concept (E = F/q) - The electric field (E) is the force per unit test charge, showing how a charge "feels" its surroundings. Field lines map out these invisible pushes and pulls, helping you visualize where a test charge would speed up or slow down. Physics Classroom
  7. Know the law's limitations - Coulomb's Law fails for moving charges at relativistic speeds and for complex charge distributions that aren't pointā€‘like or spherical. In those cases, you'll need to apply Maxwell's equations or magnetic field concepts. Wikipedia
  8. Learn about permittivity of free space (Īµā‚€) - Īµā‚€ appears in the denominator of the force formula via k = 1/(4Ļ€Īµā‚€) and sets the baseline "stiffness" of electric fields in a vacuum. It's a fundamental constant that ties electrical forces to the fabric of space itself. Wikipedia
  9. Convert units like a pro - Always switch microcoulombs to coulombs (1 Ī¼C = 1Ɨ10ā»ā¶ C) and centimeters to meters (1 cm = 0.01 m) before plugging into formulas. Skipping this step is the fastest way to get the wrong answer! GuruMuda
  10. Sharpen your skills with online quizzes - Regular practice tests boost your speed and confidence under exam conditions. Challenge yourself with timed drills and instant feedback to become a Coulomb's Law ninja! PhysQuiz
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