What is Electrostatic forces: Definition and 42 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,















{\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. jackiepollock

    B Problems regarding electrostatic forces in everyday levitation

    Hello! I'm reading this part of the A-level physics book and finding a few places that I couldn't wrap my head around. They are underlined. 1) When saying oxygen, is it saying that oxygen is the most abundant element in the shoe atoms? 2)I am not too sure why the force per atom is shared...
  2. T

    I Charged particle acceleration across a potential

    Hello, I haven't been able to find the answer to this anywhere. When calculating the energy gained by a particle that is accelerated across the gap of two cavities (e.g. Dees in a cyclotron, or charged cylindrical cavities of a linear accelerator), does one need to take into account the size of...
  3. Sunanda

    Electric Potential due to a single point charge

    Please refer to the image attached. So, my doubt is: While calculating dW in the derivation, we know this work is being done by external force, because only then the unit positive charge can be made to move towards the charge +Q. So dW should be equal to Fext.dx but here in the book it is shown...
  4. M

    Electrostatic Forces in Equilateral Triangles

    Homework Statement I've encountered a question about electrostatic forces on vertices of an equilateral triangle and I believe that I solved it correctly but my Physics teacher has marked it as incorrect. Am I correct? Amy clue why my Physics teacher marked it wrong? This is the question and...
  5. C

    Work of external forces and electrostatic potential energy

    Homework Statement Two metal spheres of equal radius ##R## are placed at big distance one from the other. Sphere 1 has total charge ##q## and sphere 2 has no charge. The two speheres are moved one towards the other until they touch, then they are moved again far away one from the other. What is...
  6. seb7

    Electrostatic Forces: Attraction vs Repulsion

    Hi, two questions: Does the same energy put into an attraction force give the same force as a repulsion force? I am wondering if one is measuring slightly weaker than the other. ie. If I measure the positive/negative attraction force, is the positive/positive repulsion force as strong when...
  7. S

    Physics Homework Question on Electrostatic forces

    Homework Statement Charge is distributed on the surface of a spherical balloon (an insulator). A point particle with charge q is inside. If polarization effects are negligible the electrical force on the particle q is greatest when: a. it is near the inside surface of the balloon b. it is at...
  8. mcaay

    Electrostatic forces in plastic bags

    I found a book which suggests that the reason why plastic bags are sometimes hard to open (which feels like they were glued) is electrostatic forces, but no matter how I look at this, I can't come up with any explanation. Is the book correct? I understand insulators and conductors, how charges...
  9. I

    Electrostatics- Charged Identical Spheres

    In electrostatics, why is it that identical spheres that are touched for a brief moment or connected by a conducting wire (wire not gaining any charge) should have an equal charge? Why is that they come in an equilibrium of charge? For example - If we take 2 identical spheres one bearing a...
  10. J

    Electrostatic Force Between Proton and Neutron?

    After calculating the force upon an electron and a force upon a proton in the atom of hydrogen, my result was a force of ≈8.2x10-8 Newtons acting upon the electron and proton each. If found this by using the formula Fe = (ke q1q2)/r2 Taking this number, I then applied it in the formula F = ma...
  11. kostoglotov

    Simple application of Coulomb's Law/Equation

    Homework Statement Two pieces of copper weighing 10 grams each are 10 cm apart and 1/1000 electrons are transferred from one to the other. Find the force of electrostatic attraction between them.Homework Equations [/B] Molar mass Cu: 63.5 g/mol \frac{1}{4\pi \epsilon_0} = 9 \times 10^9...
  12. Arjang Sh

    Can I Control Electrostatic Levitation with a Power Supply?

    Hello I need some advice about electrostatic levitation concept and am trying to make an experimental setup for that. Consider two parallel plates with the same sign charge and the bottom plate is fixed in place. Therefore there will be a repulsive force which pushes the upper plate...
  13. Arjang Sh

    Electrostatic repulsive force between parallel plates

    Hi I was thinking about two parallel plates with same charges (there's no electrical field between them). How can we calculate the repulsive force? Does anyone have any ideas besides numerical integration? Thanks
  14. Y

    Three charges located on a straight line

    Homework Statement Three charges, Q1, Q2 and Q3 are located on a straight line. The charge Q3 is located 0.169 m to the right of Q2. The charges Q1 = 1.56 μC and Q2 = -3.03 μC are fixed at their positions, distance 0.268 m apart, and the charge Q3 = 3.18 μC could be moved along the line. For...
  15. H

    Electrostatic forces and distance when considering changes in potentia

    Question: Relevant formulas: kei + pei = kef + pef U = kqq/r Attempt at solution: I thought that as distance increases potential energy would go down and so that energy would have to go to the kinetic energy of the gasses, so kinetic energy would increase. This is consistent with the...
  16. D

    Solve Electrostatic Forces Homework: Tension & Charge

    Homework Statement Two 0.115-gram pith balls are suspended from the same point by threads 22.0 centimeters long. When the balls are given equal charges, the two strings form an angle between them, and the balls come to rest 15.0 centimeters apart. Neglect the mass of the thread. What is the...
  17. G

    Chemistry Intramolecular, intermolecular, electrostatic forces

    I'm getting a bit confused as to what each force refers to. Correct me if I am wrong, Intermolecular forces (also referred to as electrostatic forces), are forces that exist between molecules. These forces can very in strength, strongest in liquids, relatively weaker in liquids, and almost...
  18. P

    Electrostatic forces between multiple particles

    So I was reading my textbook and it says that we are given a situation where two particles of the same charge are separated by the distance 0.0200m. Another particle of the opposite charge is then placed in between the other two particles, 3/4 the distance mentioned away from one and thus 1/4...
  19. P

    Overcoming Electrostatic Forces for Fusion: Can a Faraday Cage Help?

    The most difficult aspect of hydrogen fusion is overcoming the electrostatic forces that cause the hydrogen nuclei to repel each other. Would it be possible to place one of the nuclei inside some conducting sphere like a Buckminsterfullerene so that the fullerene acts as a Faraday cage? The...
  20. Roodles01

    Coulomb: Electrostatic forces

    I am working on the following. A point charge of √3Q is at point (3a, a, 2a) Find charge at (2a, 2a, 3a) I'm using Coulomb's Law E(r) = q / 4∏ε0 (r-r0)3 ([B]lr-r0l[B] & can get through most of it, but looking at my book I can't see why the last step occurs. See attachment. I can find r-ro &...
  21. M

    Electrostatic Forces of an Equilateral Triangle

    Homework Statement Three point charges are located at the corners of an equilateral triangle as in the figure below. calculate the net electric force on the 7-nc charge. Each sides are .5 m. (q1=7μc) (q2=2 μc) (q3= -4 μc) ___1 __/__\ 2/____\3 Homework...
  22. C

    Coulomb's Law and Electrostatic Forces Problem

    Homework Statement Three charges are arranged as shown in the picture I attached. Find the magnitude and direction of the electrostatic force on the charge at the origin.Homework Equations I know that Coulomb's Law must be applied.The Attempt at a Solution I've drawn a force diagram with FCB...
  23. A

    Equillibrium of electrostatic forces of 2 charges on a 3rd

    Homework Statement Two particles lie on the x axis. The first particle is at the origin with a charge of +1.6uC and the other has a charge of -3.1uC and is +10.5cm away. If particle 3 of unknown charge q3 is to be located such that the net electrostatic force on it from particles 1 and 2...
  24. hanley93

    About Electrostatic Forces on Parallel Plate Capacitor

    I've been thinking about this for a while, and I think people of PF will be able to answer it haha In parallel plate capacitor, we charge the capacitor by connecting a power supply/battery. Then, after few minutes, the capacitor is fully charged with different signs, + and -. With that...
  25. R

    Electrostatic Forces on Three Hypothetical Parallel Planes

    Say there is are three hypothetical infinite parallel planes with charges on it. So let's imagine the three planes from left to right, or planes one, two and three. Plane-three is fixed to the reference frame. Plane-one and plane-two have a fixed separation distance between each other, but...
  26. N

    Square- electrostatic forces

    Homework Statement There are four charges, each with a magnitude of 2.1 µC. Two are positive and two are negative. The charges are fixed to the corners of a 0.25 m square, one to a corner, in such a way that the net force on any charge is directed toward the center of the square. Find the...
  27. R

    Superpositions of electrostatic forces

    Homework Statement Three particles P1, P2, and P3 are located at the points (−2.00, −1.00), (0, 2.00), and (3.00, −1.00), respectively. P1 has a charge of 5.00 μC, but the charges of P2 and P3 are unknown. However, the three particles exert no net force on a charged particle that is placed at...
  28. K

    Spring and electrostatic forces

    Homework Statement You have a lightweight spring whose unstretched length is 4.0 cm. You're curious to see if you can use this spring to measure charge. First, you attach one end of the spring to the ceiling and hang a 1.0 g mass from it. This stretches the spring to a length of 5.0 cm. You...
  29. K

    Electrostatic forces helpp

    Electrostatic forces helpp! Homework Statement Two spheres, each having a mass of 50.0 mg, are suspended from a common point by massless threads 50.0 cm long. One of the spheres have been given a charge twice that of the other. The strings make an angle of 6.00 degrees. What are the charges...
  30. K

    Electrostatic Forces and Coulombs Law Question

    Homework Statement Two small, positively charged spheres have a combined charge of 5.4 x 10-5 C. If each sphere is repelled from the other by an electrostatic force of 1.04 N when the spheres are 2.2 m apart, what is the charge on sphere with the smaller charge? Homework Equations...
  31. T

    Can electrostatic forces explain electron configurations?

    I've been studying basic atomic structure-- shells, subshells, orbitals, the four quantum numbers, the periodic table, etc. I've seen diagrams of "atomic structure" that show arrangements of electrons: 1s2, 2p2, 2p6 etc. and I understand how the configurations are derived from the quantum...
  32. T

    Can electrostatic forces explain electron configurations?

    I've been studying basic atomic structure-- shells, subshells, orbitals, the four quantum numbers, the periodic table, etc. This is in a chemistry book, but if my question belongs in the physics forum please let me know. I've seen diagrams of "atomic structure" that show arrangements of...
  33. D

    Electrostatic Forces on Particles

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  34. H

    Capacitors,dielectrics and electrostatic forces

    hi in what direction does the electrostatic force act when we insert a dielectric within a capacitor? and when we remove the dielectric? supposedly they act in opposite directions in each case, and either push or pull the dielectric out or into the capacitor. i m not able to understand how the...
  35. A

    Electrostatic forces and the principle of superposition

    1. Explain what is meant by statement that electrostatic forces obey the principle of superposition? 2. what does it mean to say that physical quantityis (a) quantized or (b) conserved.
  36. A

    Electrostatic Experiments: Why Not Work on Humid Days?

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  37. B

    Question about electrostatic forces

    Two identical conducting spheres, fixed in place, attract each other with an electrostatic force of 0.0864 N when their center-to-center separation is 70.6 cm. The spheres are then connected by a thin conducting wire. When the wire is removed, the spheres repel each other with an electrostatic...
  38. S

    Force Diagram of Electrostatic Forces

    Homework Statement Two uniformly charged spheres are firmly fastened to and electrically insulated from frictionless pucks on an air table. The charge on sphere 2 is three times that on sphere 1. Which force diagram correctly shows the magnitude and direction of the electrostatic forces...
  39. A

    Potential energy and electrostatic forces

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  40. E

    Help Needed: Modeling Beam Bending with Electrostatic Forces

    Hey-- I'm trying to model the bending of a beam due to electrostatic forces. (Femlab does offer this model on their website, but the module I'd need to run it costs $600!) I have no problem modeling a beam bending, and I have no problem creating a parallel plate capacitor, but when I...
  41. I

    Electric fields and electrostatic forces

    Electric fields and electrostatic forces (1 question) I was wondering if someone can show me how to answer this problem. Thank you. 1)Two charges are placed on the x-axis, an unknown positive charge at x=0 cm and a negative 8.642e-6 C charge at 2.993 cm from the origin. Calculate the...
  42. S

    Net Charge of -59uC: #Electrons & Mass Increase

    A person accumulates a net charge of -59uC, how many excess electrons does this person get and by how much does her mass increase?