What is Coulombs law: Definition and 100 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,





|

F

|

=

k

e






|


q

1



q

2



|



r

2






{\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.

View More On Wikipedia.org
  1. M

    Help with Coulomb's law: Net electrostatic force

    I tried just calculating the force with Coulomb's law, then calculating the forces for each vector individually and adding, but I got it wrong both ways
  2. Z

    Find the electric field on the surface of a sphere using Coulomb's law

    Note that the solution is 5625 V/m in z direction which is found easier using Gauss' law, but I want to find the same result using Coulombs law for confirmation. Lets give the radius 0.04 the variable a = 0.04m. ##\rho## is the charge distribution distributed evenly on the surface of the...
  3. B

    Hanging pith balls on a thread...charge, Fg, Fe and tension

    Homework Statement Two pith balls each have a mass of 1.0g and equal charges. One pith ball is hung from an insulating thread. The other is fixed at a horizontal distance of 3.0cm from the first, The first hangs at an angle of 30.0° from the vertical. Find: a) the gravitational force on the...
  4. S

    Coulomb's Law in 3D: Find Electric Force & Field

    Homework Statement q1= 5 x 10^-6C position (1;2,-1) q2= -3 x 10^-6 C position (-2,1,3) a) what is the electric force caused by q2 on q1? (vector notation) b) what is the electric field at (0,0,0) Homework Equations F = kq1q2/r^2 E= F/q The Attempt at a Solution I really don't...
  5. A

    Possible variables for Coulombs Law?

    COULOMBS LAW F= K Q1 Q2 / R2 How would I solve for Q1 and Q2?
  6. 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...
  7. A

    Coulombs law and particle charges

    Homework Statement An electron and another particle experience an attractive force of 0.0096 N when they are 0.001m apart. what is the charge of the other particle q1= -1.602E-19 F=-0.0096 r=0.001 2. Relevant equation how do you find q2 out to solve the equation The Attempt at a Solution
  8. A

    What is the Force Between Two Protons 1.0m Apart?

    Homework Statement two protons are 1.0m apart. find the force acting on them. q1= 1.602E-19C q2= 1.602E-19c Homework Equations i just don't get how to work it out The Attempt at a Solution ive got this far up to now [(9E+9)(1.602E-19)(1.602E-19)]/(1.0)². don't know where to go from here
  9. P

    Why Are The Units of Coulombs Law What They Are?

    Why are the units of force used when applying coulombs law (N-M^2)/(C^2)? This is actually a three part question. 1. Why are the units of the permitivity constant (C^2)/(N-M^2)? 2. Why do Q1 and Q2 not contribute to the final units? Each charge is measured in coulombs, but those units don't...
  10. RoboNerd

    Question on finding work done on charge

    Homework Statement Homework Equations coulomb's law The Attempt at a Solution Hi everyone. I understand their approach with the integration to find the amount of work that "a person" would have to do to bring the charge q3 from infinity to its current position. I understand...
  11. Anthony Santelices

    Finding energy in a 4 object charge system

    Homework Statement An object with charge +2.0×10−5 C is moved from position C to position D in the figure (Figure 1) . q1 = q3 = +10.0×10−5 C and q2 = −20.0×10−5 C. All four charged objects are the system. Here's a picture to the problem Homework Equations $$ F = \frac {kq_1 q_2}{r^2} $$ $$...
  12. U

    Charge inside and outside conducting shell

    A thin metallic spherical shell contains a charge Q over it. point charge +q is placed in side the shell at point T separated from the centre by a distance a. Another point charge q1 is placed outside the shell at a distance b from the centre find the electric field at the centre due to the...
  13. K

    How many electrons make up a charge of -15.0 uC?

    So I've already got some help on this one, now I have a different question pertaining to this equation. I know N=q/e e=-1.6x10^-19 q=-15x10-6 so I tried: N=(-15x10-6)/-1.6x10^-19 N=-156/-1.6x10^-19 N=9.74 ~that was wrong So I thought maybe this: N=(-15x10-6)/-1.6x10^-19 N=--60/-1.6x10^-19...
  14. C

    How Do You Apply Coulomb's Law to Calculate Forces in a 3D Coordinate System?

    Homework Statement An xyz coordinate system contains three charged particles: particle 1, q1=− 6.5μC , at (4.0 m,-2.0 m, 0); particle 2, q2 = 12μC , at (1.0 m,2.0 m, 0); and an electron at at (-1.0 m, 0, 0). Determine the x, y, z components of the vector sum of the vectors of the electric...
  15. 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...
  16. S

    Finding the electric field at point p in this formation?

    Homework Statement What is the magnitude of the electric field at point p due to the four point charges shown? The distance d is between charge centers. Homework Equations Electric Field = kq/d^2 Coulomb's Law = k(q1q2)/d^2 The Attempt at a Solution I don't know how to go about solving this...
  17. S

    Net Electric Force Homework: Find Negative Charge Position

    Homework Statement [/B] In the above figure, if Q1 and Q2 are positive, where could a negative charge be placed and have a vertically upward net force on it? Homework Equations F = k|q||q| / (r^2) The Attempt at a Solution I wrote the force equations for the negative charge and both positive...
  18. julianwitkowski

    1D Collision / Charges / Coulomb's Law

    Homework Statement Two frictionless pucks are placed on a level surface with an initial distance of 20.0 m. Puck 1 has a mass of 0.80 kg and a charge of + 3 E-4 C while puck 2 has a mass of 0.4 kg and a charge of +3 E-4 C. The initial velocity of puck 1 is 12 m/s [E] and the initial velocity...
  19. 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...
  20. R

    Coulomb's law theoretical hypothetical question

    The Scenario: Let's say one could have a lot of cations produced from a gas in a single plane contained in a 1 square foot area (like a fence around sheep). This plane of cations is over another one that is on the ground. So basically two layers of Cations in a tall hollow cube like...
  21. M

    Flux Through a Non-Concentric Sphere

    Homework Statement Assume I want to calculate the electric flux through a spherical surface centred at point P with radius R which contains a point charge Q, that is not concentric with the spherical surface. Here, I can no longer assume that ∫∫sEdA = E.A, and I have to calculate the value of...
  22. rpthomps

    Electrical Energy and Coulombs Law

    Homework Statement Charge q1 is fixed to a spring with constant k_s. It is at equilibrium initially and located r+x away from q2 (which is oppositely charged). The charge q1 is released and allowed to move closer to q2, pulling the spring and stopping. Now the charges are only r distance away...
  23. P

    Please verify my solution (Electric field cylinder)

    Homework Statement Finding the electric field outside of a uniformly charged solid cylinder, of length L and radius R, at any point of its axis. Homework Equations \displaystyle{ \vec{E} = \frac{1}{4 \pi \varepsilon_0} \int \rho(r') \frac{(\vec{r} - \vec{r'})}{\left| \vec{r} - \vec{r'}...
  24. C

    How Can We Solve this Second Order ODE for Electron Behavior?

    Homework Statement I'm taking an online introductory chem course, and while explaing the failure of classical mechanics to describe electron behavior, the teacher brought up the following ode which is based on Newton's second law and coulombs law: -e^2/4(pi)(epsilon-nuaght)r^2=m(d^2r/dt^2)...
  25. Q

    Calculating the initial charge on an object

    Homework Statement Neutral metal sphere A, of mass 0.10kg hangs from an insulating wire 2.0m long. An identical metal sphere B, with charge -q, is brought into contact with sphere A. The spheres repel and settle(a picture just imagine a right angle triangle with 2 objects A and B at the...
  26. Q

    Optimal Placement for Net Zero Electrical Force in a System of Charged Spheres

    Homework Statement Two small spheres with charges 1.6*10^-5 C & 6.4*10^-5 C, are 2.0m apart. The charges have the same sign. Where, relative to these two spheres, should a third sphere, of opposite charge 3.0*10^-6 C, be placed if the third sphere is to experience no net electrical force? Do we...
  27. Q

    The equation to calculate the tension in terms of Coulombs Law

    Hello I was wondering what the equation is to calculate the tension in terms of coulombs law an example problem would be http://gyazo.com/1319551eb367990c75ee0a782e38a2c2
  28. M

    Coulomb's Law formula help

    How do you calculate compute the the magnitude of the total force of three charges and also the angle it makes with the x-axis? Knowing the magnitude and also the 2d co ordinates of the charges. I have deliberately not given any specific values because this is not homework its a question from...
  29. johann1301

    Coulombs Law & Space-Time: Exploring the Connection

    Im reading about Coulombs law in my textbook. It states that: "The forces between to charged particles are proportional with the charges Q1 and Q2, and inversely proportional with the square of the distance r between them. F=kQ1Q2/r2 The forces acts along the straight line between...
  30. C

    Discrepancies with Coulombs law?

    Homework Statement E obeys Coulombs law, i.e. E is proportional to 1/r^2. However, between a parallel plate, E = constant and in coaxial cylinders E is proportional to 1/r. What is the explanation for these discrepancies? Homework Equations The Attempt at a Solution I think that...
  31. K

    Calculating Net Force and Electric Field Using Coulomb's Law - Homework Question

    Homework Statement This is the charge distribution:B | | | 2.0 m | | A------------C 2.0 m A = 2.0*10^-5 C B = -3.0*10^-5 C C = -3.0*10^-5 C a) Find the net force on the charge b) what is the net electric field acting on the chargeHomework Equations FE=kq1q2/r^2 electric field =...
  32. F

    How Many Electrons Are Needed to Accelerate Two Charged Spheres at 25g?

    I know almost this exact thing has been asked before but even after looking at the other posts I still can't figure out what I'm doing wrong. Homework Statement Two very small 8.05-g spheres, 11.0 cm apart from centre to centre, are charged by adding equal numbers of electrons to each of...
  33. skate_nerd

    Coulombs law, initial speed to collide with other nucleus

    Homework Statement A helium nucleus has radius rHe = 1.9 fm, mass m = 6.6 × 10-27 kg, and charge +2e. A gold nucleus has charge +87e and radius rAu = 7.0 fm. What initial speed must a helium nucleus have if it is to come into contact with a fixed gold nucleus in a head on collision...
  34. R

    My brain has been shocked by this problem dealing with charges and Coulombs law

    My brain has been shocked by this problem dealing with charges and Coulombs law :( This is what I did... F = k*q1*q2/r^2 F = [ (8.99 * 10^9)(4.9 * 10-9)(6.0 * 10^-9) ] / (0.295)^2 F = 0.000000264 / 0.087025 F = 0.0000003034 F = 3.034 * 10^-7 N F = k*q1*q3/r^2 F = [ (8.99 *...
  35. S

    Coulombs Law with vectors question help, test tomorrow.

    1. Homework Statement [/b] 1. Charge A (-2uC) is 0.10m left of charge B (+3uC), with charge C (+4uC), 0.075m below charge B, forming a right angle triangle with the right angle at B. Find the net electrostatic charge on C if its confusing the 0.10 is the opposite of the hypotenuse with the...
  36. A

    Electromagnetics coulombs law and field intensity

    Homework Statement The circular region, ρ < a, z= 0, carries a uniform surface charge density ρ ( subscript s). Find E at P(0,0,h), h > 0. Homework Equations Coulombs law Field of a line charge and field of a sheet charge.The Attempt at a Solution I'm not sure what they are asking for , but my...
  37. Pruddy

    Coulombs Law: magnitude of the force between two point charges

    Homework Statement Determine the magnitude of the force between two point charges, Q1 = -2e located at (-3.60 cm, +4.10 cm) and Q2 = -8e located at (-0.60 cm, -8.60 cm). Give your answer in the form "a.bc x 10^(y) N". Homework Equations F = kq1q2/r2 The Attempt at a...
  38. D

    Finding Q1 and Q2 in coulombs law

    0.36=(K)x(Q1xQ2/0.25^2) Find Q1 and Q2 if Q1=3(Q2) Using the solve function in my calculator I get Q1=2.74x10^-6 and Q2=9.13x10^-7 I would just like to know whether my answer is correct and how to do it in a calculator without using the solve function. Thanks in advance. Edit: Yep sorry...
  39. S

    Deriving Coulomb's Law with Virtual Photon Exchange Theory: Complete Explanation

    How the virtual photon exchange theory be used to derive completely Coulombs Law related to electrostatic field? Complete derivation means derivation involving charges and distance
  40. G

    Coulomb's Law and Electric Fields for a Triangle of Charges

    Homework Statement Consider three charges q1 = 4.3 nC, q2 = 6.6 nC, and q3 = -2.3 nC, arranged in a triangle as shown below. (a) What is the electric force acting on the charge at the origin? N, ° counterclockwise from the negative x-axis (b) What is the net electric field at the...
  41. G

    Calculating Electric Force with Coulomb's Law: Glass and Rubber Ball Example

    Homework Statement What is the electric force between a glass ball that has +2.8 µC of charge and a rubber ball that has -4.8 µC of charge when they are separated by a distance of 4.5 cm? 2. Homework Equations F=k*Q1*Q2/r^2 3. The Attempt at a Solution -59.6507...
  42. J

    Coulombs Law - Finding Force When Altering Distance

    Homework Statement If two charged bodies attract each other with a force of 1 Newton, with what force will they attract each other if the distance between them is reduced to one-half of its original size? (The “Newton,” abbreviated by the letter N, is the unit of force in the metric system...
  43. P

    How Do Charges Transfer and Affect Coulombic Forces?

    Homework Statement I don't understand how to apply coulombs law when there are 3 balls, giving each other charge. I know that the answer for part a) is 0.02N and part b) is 0.005 N but have no idea how to get these answers. Homework Equations Two identical plastic balls A and B with a...
  44. K

    College Physics II Charge/ Coulombs Law

    Homework Statement A point particle that has a charge of 14.5 µC is located at x = 0, y = 0 and a point particle that has a charge q is located at x = 11.6 cm, y = 0. The electric force on a point particle that has a charge of 5.8 µC at x = 23.2 cm, y = 0 is -(19.7) N ihat. Determine the...
  45. L

    Coulomb's Law and Final Angle of Dust Cobweb

    (I posted this in the wrong section earlier, hopefully i got it right this time...) 1.Homework Statement A dust cobweb is drawn from an initial vertical position toward a nearby wall by an electrostatic force. Assume the cobweb to be like a single dust ball of mass 2.0 x 10^-7g suspended on...
  46. B

    Difficult Coulombs Law questions

    Homework Statement Q1.Two Charges, -Q and -3Q, are a distance l apart. The two charges are free to move but don't because there is a third charge nearby. What must the third charge be and where must it be placed for the first two to be in equilibrium? Homework Equations Coulombs Law: F =...
  47. B

    Exploring Coulombs Law Extended: Derivations, Uses, and Limitations

    My physics professor gave us an extended version of coulombs law which includes terms to account for moving charges. He then used (or rather compared) this law to the Lorentz force equation to give us a feel for the electrical forces generated by moving charges as he introduced us to magnetism...
  48. R

    How Do I Calculate Coulomb's Law for Fractional Electrical Charges?

    The law I am talking about is F=K* (qa*qb / r2) I know the values of all but I have a question on the q's which represent the electrical charges... If the charge is +2/3 do I plug in the fraction 2/3 in the q's spot? is this the numerical number I use? PLEASE HELP!
  49. A

    Coulombs Law. Calculate Charge Magnitude and Direction

    Homework Statement Three charges are arranged as shown in the diagram below. Their magnitudes are: q1 = +2.5 x 10^-17 C q2 = +3.0 x 10^-17 C q3 = +3.5 x 10^-17 C (its a right angle triangle, with 50 cm as the hypotenuse, 40 cm as the horizontal, and 30 cm as the vertical) Figure image...
  50. A

    Coulombs Law & Electric Charges

    Homework Statement Two negative electric charges, (Charge A on the left, and Charge B on the right) each with a charge of 3.0 x 10-5 Coulombs are fixed at a distance of 2.9 meters from each other. Find the electric force of charge A on charge B. (Don't forget, if the force points to the left...
Back
Top