What is Coulomb's law: Definition and 403 Discussions

Coulomb's law, or Coulomb's inverse-square law, is an experimental law of physics that quantifies the amount of force between two stationary, electrically charged particles. The electric force between charged bodies at rest is conventionally called electrostatic force or Coulomb force. The law was first discovered in 1785 by French physicist Charles-Augustin de Coulomb, hence the name. Coulomb's law was essential to the development of the theory of electromagnetism, maybe even its starting point, as it made it possible to discuss the quantity of electric charge in a meaningful way.The law states that the magnitude of the electrostatic force of attraction or repulsion between two point charges is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them,





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{\displaystyle |F|=k_{\text{e}}{\frac {|q_{1}q_{2}|}{r^{2}}}}
Here, ke is Coulomb's constant (ke ≈ 8.988×109 N⋅m2⋅C−2), q1 and q2 are the signed magnitudes of the charges, and the scalar r is the distance between the charges.
The force is along the straight line joining the two charges. If the charges have the same sign, the electrostatic force between them is repulsive; if they have different signs, the force between them is attractive.
Being an inverse-square law, the law is analogous to Isaac Newton's inverse-square law of universal gravitation, but gravitational forces are always attractive, while electrostatic forces can be attractive or repulsive. Coulomb's law can be used to derive Gauss's law, and vice versa. In the case of a single stationary point charge, the two laws are equivalent, expressing the same physical law in different ways. The law has been tested extensively, and observations have upheld the law on the scale from 10−16 m to 108 m.

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  1. J

    Calculating Electric Field Using Coulomb's Law

    Homework Statement Homework Equations Ex=1/k*1/(a^2/2)*1/(sqrt2)*cos(theta)*(sum of charges) Ey=1/k*1/(a^2/2)*1/(sqrt2)*sin(theta)*(sum of charges) The Attempt at a Solution So first off I can see that I don't need to calculate the force in the x direction as each q cancels out when...
  2. MetaUniverse

    3 basic question about Coulomb's Law

    Hello everyone! I'm currently trying to calculate electric forces between two objects, so for that I of course need Coulomb's Law. I understood its equation (etc.), but there are 3 things that I haven't found out yet: -How exactly can you find out or calculate what amount of charge an object...
  3. H

    Coulomb's Law in Two Dimensions

    Homework Statement Three charges, q1, q2, and q3, lie in a plane, as shown below. Find the net force on charge q2 (please refer to attachment for diagram) Homework Equations F= k x q1q2/R^2, knowledge of trig functions and separating x and y components The Attempt at a Solution So I found the...
  4. C

    Coulomb's law in its vector form?

    sorry I have use the image I made. Since I don't know how to perform the formula on forum :( This is the problem I am having.
  5. David Anton

    Measuring charge (or potential) with electroscope?

    I am trying to measure the charge(or voltage) of a positively charged sphere by touching it with a non- calibrated electroscope. I am getting consistent results in the separation(or angle) between the metal leaves, but I don´t know how to calculate the voltage between the leaves from there. I...
  6. P

    I Experimental check of photon mass and Coulomb's law

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  7. A

    Coulomb's law vs Electric Field

    Homework Statement I just wanted to make sure I understood the difference between the two. Coulombs law is the force between two charges. Two charges that are physical(maybe not the right word) located on some axes. We can use the equation F=k(q1 * q2 * r(hat))/r^2 r^2=|r| = |x-x'| where r hat...
  8. Mohammed Alqadhi

    Coulomb's Law: Maximum Force & Distance?

    According to Coulomb's law, the electric force between two, equal in magnitude and opposite in direction, charges depends on the distance between them, and as they get close to each other, the force increases and the distance decreases. At the position when they get stuck with each other, the...
  9. Blockade

    Is the total electric field of two opposite charges 0?

    Let's say you have two particles that are the same in magnitude but have opposite charges like the equation down below: E1 = -q*k/r^2 E2 = q*k/r^2 ETotal = q*k/r^2 + -q*k/r^2 = 0 Does this mean that the electric field of both these charges cancel out each other? Then what is the electric...
  10. D

    Consider the configuration consisting a +q charge....

    and two -q charges aligned along the x-axis as follows... -q__________q__________-q <--- the space between them being d a) Suppose the +q charge is displaced perpendicularly by a small vertical distance dy. What is the total force F acting on it? Taylor expand your answer to leading order in...
  11. P

    Vector Confusion In Applying Coulomb's Law

    Homework Statement http://imgur.com/48cLE6q Homework Equations Coulomb's law The Attempt at a Solution I can follow most of this problem, but I am unsure where the constants in front of the trig functions are coming from. Why is it 2cos(135), 1cos(45), 2cos(-45), etc?
  12. A

    Finding the Electric Field at the Midpoint of two rings

    Homework Statement Hello, Two 10-cm-diameter charged rings face each other, 20 cm apart. The left ring is charged to -22 nC and the right ring is charged to +22 nC . What is the magnitude of the electric field E⃗ at the midpoint between the two rings? Homework Equations [/B] E = Kq/r^2 K =...
  13. L

    Solving an equation involving Coulomb's law

    Homework Statement Hi Members, I have solved an equation involving Coulomb's law in two ways and have posted the images of the same. I get two types of equations. Please help me to find where i gone wrong? Homework EquationsThe Attempt at a Solution
  14. J

    How Can I Determine the Value of Charges in Coulomb's Law?

    Hello, I am pretty new to physics. I have no formal education on physics, and I have been studying it on my own out of curiosity and fascination. Please correct me if anything that I say is wrong and assume I know nothing. Math is also not my strongest skill, but I am trying to become better...
  15. S

    E-field of a Semi-spherical charge distribution with a hole

    Homework Statement Using direct integration, compute the electric field at the point (0,0,Z) of a semi-espherical (z > 0) charge distribution of radius R < Z and density ##\rho=constant## having a spherical hole of radius ##r_h<R## centered at (0,0,##r_h##). Homework Equations Coulomb's law...
  16. A

    Coulomb's Law and the Force Between Charged Bodies Across Vast Distances

    Homework Statement We know that coulomb's law describes the force between two charged bodies as proportional to the magnitudes of the charges and inversely proportional to the square of the distance. Of course, like charges repel and unlike attract. Now theoretically, if we placed two...
  17. ssnapier

    Working on Coulomb's Law lab, what is this symbol?

    I just need to know what I am being asked for here, I don't recall seeing this symbol before. Is this net force?
  18. Dr. Who

    Finding number of charges using Coulomb's Law

    Homework Statement Please refer to the image; problem-1. My theory is that there are two spheres 'A' and 'B', where 'A' is (partially and primarily) positively charged, and 'B' is (partially and primarily) negatively charged. The magnitude of negative charge is greater than the positive charge...
  19. jk22

    How does Coulomb's law change in 3+1 dimensional spacetime?

    The power law of Coulomb depends on the dimension treated . It is $$1/r^{n-1} $$ where n is the dimension. In n=3 we get the inverse square law. How does this go into considering now spacetime 3+1 dimensional ? Would it modify the law and how ?
  20. CARNiVORE

    Maximizing Electrostatic Force on a Moving Particle

    Homework Statement In the figure particles 1 and 2 of charge q1 = q2 = +24.00 × 10-19 C are on a y axis at distance d = 18.0 cm from the origin. Particle 3 of charge q3 = +17.60 × 10-19 C is moved gradually along the x axis from x = 0 to x = +6.47 m. At what values of x will the magnitude of...
  21. Vinay080

    Justification for the acceptance of Coulomb's law

    I read the Coulomb's first memoir on Electricity and Magnetism (Louis L. Bucciarelli english translated version), and found it to contain only three trials (as complained by many) to reach the conclusion of a 1/r2 equation for the force. And many seems to have also complained for not having able...
  22. A

    What does "stationary charges" mean in Coulomb's law?

    Hello. I am an intro Physics student and this is my first post here. In Coulomb's law the charges are said to be stationary. I need some clarification about what does it mean for two charges to be stationary: A. Does it mean that the charges are not moving with respect to each other? (But...
  23. Seismic101

    Units of P1 and P2 in Coulomb's Law

    - What are the units of P1 and P2 in Coulomb's law for magnetic poles? (picture attached). - What is the accurate name of 'P' : magnetic pole strength? Magnetic pole intensity? PS: Sorry if my questions are too basic for this forum- I am not a Physicist.
  24. 1729

    Problem involving Coulomb's law

    Homework Statement A big metal sphere has radius ##r## and charge ##Q##. The distance between a certain point charge and the surface of the sphere is equal to ##s##. The magnitude of the force exerted on the point charge is inversely proportional to: A) ##s^2## B) ##r^2## C) ##(s+r)^2##...
  25. rizwanibn

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    I am not getting the answer to this question as shown in the textbook. Please help...! My attempt is in the last attachment. Thanks.!
  26. D

    Coulomb's Law: Calculating the Force between Two Charged Balls

    Homework Statement A small ball has been loaded so that its charge is -2.6 nC. Another similar ball has the charge +1.2 nC. The balls are located at the distance 2.5 cm from each other . With how much force do the balls attracts each other? Homework Equations F = k * (Q1 * Q2)/r2 The...
  27. Cosmology2015

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    Hello, I have a question about the interaction between particles. Maybe it's a simple question, but it's bothering me. Consider Coulomb's law. From Wikipedia we have a simple definition to illustrate: "The magnitude of the electrostatic force of interaction between two point charges is directly...
  28. P

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    1. The problem statement, all variables and given/known }data The picture I drew is quite sad but it's the best I could do lol. I forgot to mention in the image that it's the magnitude of the net force we're looking for. Homework Equations...
  29. H

    Calculating Charge on Two Pith Balls Using Coulomb's Law | Homework Help

    Homework Statement The charge on two pith balls can be calculated by knowing their masses and observing the angle of separation between the balls. If both balls are equally charged and they are suspended by strings that are 1.0 m long, calculate that charge. Homework Equations F = k q Q /...
  30. fricke

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  31. Corey Bacon

    Net force on particle 1 due to particle 2 in vector form?

    Homework Statement Hi all, I have this quiz on MasteringPhysics, but I can't seem to get the right answer.[/B] Consider two positively charged particles, one of charge q0 (particle 0) fixed at the origin, and another of charge q1 (particle 1) fixed on the y-axis at (0,d1,0). What is the net...
  32. yeshuamo

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    Homework Statement A thin sheet in the shape of an annular semicircle has a positive surface charge density +σ as shown. What is the electric field at point P? Here is an illustration of the problem: http://postimg.org/image/630bpqwan/Homework Equations Gauss's Law: φ=Qenclosed/ε0 φ=∫E⋅dA...
  33. J

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    I will like to know how to approach to this problem: Over the x-axis is Q1=60μC Q2=-80.0μC the separation between them is 50.0cm. There is a point A on the y-axis 40.0 cm above Q1, and a point B 40.0cm above Q2. I want to know how to approach to find the direction and magnitude of the Net...
  34. nomadreid

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    Given that (a) the electrostatic force is inversely proportional to r2 (b) that the electron is (when it is determined) a point (c) that the repulsion for an electron to itself is therefore r=0 (d) that r=0 would naively end up with infinite force What is the way out of this problem? Thanks
  35. Z

    Where on the X-Axis is the Net Electric Force Zero?

    1.An electric charge q1 (-e) is located at the origin. A second electric charge q2 (-4e) is located at a distance d from the origin on the x-axis. A third charge q3 (+e) is located a distance x, which is less than d, on the x-axis between q1 and q2. In terms of d, what is the distance x where...
  36. L

    Can you merge these equations and get acceleration

    m*a=k*Q1*Q2/r equalizing Newton's first law and coulomb's force to get acceleration of the specific charged body.
  37. S

    Magnitude and Direction of an (E) Electric field of a square

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  38. S

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    Homework Statement This problem is taken from 'Introduction to Electrodynamics' by David Griffiths. (a) Twelve equal charges, ##q##, are situated at the corners of a regular 12-sided polygon (for instance, one on each numeral of a clock face). What is the net force on a test charge Q at the...
  39. S

    Incredibly basic Coulomb's law question - am I being silly?

    I've attached my workings... But is this correct? I can't see the fault with it. However I can't see how there will be no y-component to the force... Can someone a bit smarter than me tell me if I'm being really dim. https://flic.kr/p/sutQu4][/PLAIN]
  40. David Carroll

    Electron Capture and Coulomb's Law

    Sorry for the brevity of the post, but eloquence has never been my strong point. Here's my question: In a proton-surfeited atom, a proton captures an electron to form a neutron. Now, according to Coulomb's law, the magnitude of the electrostatic force field is equal to (kq1q2)/d2, where k is...
  41. S

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    Examine the charge distribution shown: b) What is the net electric field acting on charge 1? Attempt at the answer: E2 = Kq2/r2^2 = (9.0 x 10^9 Nm^2/C^2)(3.0 x 10^-5 C) / 2.0m^2 E2 = 6.75 x 10^4 N/C E2 = E3 ( therefore, same procedure) eNet = Sqr.rt. 6.75 x 10^4 N/C^2 + 6.75 x 10^4 N/C^2...
  42. C

    How Coulomb's Law relates to generators? (voltage)

    Homework Statement In science class, we are supposed to explain how a generator works and functions. However, we have to incorporate coulomb's law in our explanation. Homework Equations F=kQ1Q2/r^2<-- coulomb's law The Attempt at a Solution How I understood it was that a generator consists of...
  43. S

    How did Coulomb charge his spheres to verify Coulomb's law?

    We are doing an experiment to verify coulomb's law, and we are currently using a stable voltage source. However, we were assigned to do it using static electricity, and we were wondering how to establish inverse r^2 dependence if the amount of the charge on the ball isn't the same every time we...
  44. A

    Analytical Problem with Coulomb's Law

    Homework Statement Consider a parallel universe where the laws of nature as we know them are different, and aqueous solutions can have an excess charge. Two beakers are separated 1.20 meters and each contains 0.300 L of an aqueous solution of 6.40 × 10-6 M excess charge. One beaker has a net...
  45. M

    Calculating Net Force and Electric Field on Charge 1 in Coulomb's Law Problem

    Homework Statement Examine the charge distribution shown. a) Find the net force on charge 1 b) What is the net electric field acting on charge 1 (Haven't gotten to this yet. I know I won't be given the answer, however, even a hint on building intuition would be appreciated) I've plugged my...
  46. Teemo

    What is the Most Likely Product of Decomposing a Carbonate?

    Homework Statement http://i.imgur.com/Ypqcw19.png Homework Equations N/A The Attempt at a Solution Since the reaction involves the breaking of bonds in MCO3, I assume we are looking at coulomb interactions. I'd think the answer is D) BaCO3 because all the options have a 2+ charge, but barium...
  47. kostoglotov

    Three point charges with a central fourth charge

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  48. T

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  49. B

    Coulomb's law vs. Newton's law of gravitation?

    What would be the easiest way to describe the similarities and differences between the two laws, other than the fact that their formulas are built similarly and they use different measurements. Any input would be great; I am currently having a brain block! Coulombs Law:F=K (q1*q2)/r^2 Newtons...
  50. deldel

    Calculating Electric Force: Coulomb's Law Example and Solution

    Homework Statement Two identical conducting spheres of charges 3q and -q attract each other with a force of 36 x 10-3N. When they are separated by a distance of 0.2 m. The spheres are brought into contact with each other and then separated by a distance of 0.1 m. What is the magnitude of the...
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