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,





|

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. L

    Coulomb's Law, finding acceleration direction

    Homework Statement Two charges q1 = -7 and q2 = -2, both charges are fixed in place and the distance between them is 2m. Third negative charge q3 is moving along the vertical line that connects two charges. 1) net force acting on q3 = 0; where is the charge located ? 2) If charge q3 is...
  2. deldel

    Optimizing Coulomb's Law: Finding Maximum and Minimum Charges

    Hi, I'm having trouble figuring out one of my homework questions. It says " The total charge on two charged objects is Q. What must the charges on each of them be, in order that the force between them is (a) maximum and (b) minimum.Thanks guys.
  3. 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...
  4. Y

    Coulomb's Law and Electrical Fields

    Homework Statement The tine sphere at the end of the weightless thread has a mass of .60g. It is immersed in air and exposed to a horizontal electric field of strength 700 N/C. The ball is in equlibrium in the position shown. What are the magnitude adn sign of the charge on the ball? Homework...
  5. D

    Coulomb's law and two point charges question

    1. two point charges q1 and q2 with a combined charge of 20 micro coulombs are placed 3m apart. If one repels the other with a force of 0.075N calculate; the value of q1 and q22. k=8.987x10^9 F=kxq1xq2/r^2 E=kQ/r^2 E=f/q3. I've tried to work out the charge by working out the...
  6. A

    Validity of application of Coulomb's Law with moving charge?

    Hi there, I'm trying to brush up on some of my E&M and am comparing treatments of Coulomb's Law in introductory calculus-based texts with higher level material. My understanding was that Coulomb's Law (and by extension, calculation of the electrostatic force on a charged particle using F = qE)...
  7. S

    How to find the magnitude of a point charge given 2 others?

    Homework Statement Three charges are placed as shown in the figure below. The magnitude of q1 is 2.00 µC, but its sign is not known. The charge and sign of q2 is not known. We do know that q3 is +4.00 µC and the net force on q3 is entirely in the negative x-direction. a.) Deduce the signs of...
  8. 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...
  9. V

    Coulomb's Law - Calculating Net Force

    Hello all, I am new to the website and I have joined because I just started a Physics class in College and I've never done any sort of Physics and after my first day I was thrown this problem and have been looking at it for a while now and finally gave in for some sort of help. 1. Homework...
  10. julianwitkowski

    Coulomb's Law, Charges and Acceleration

    Homework Statement An electron is fired at 4.0 e+6 m/s horizontally between the parallel plates as shown, starting at the negative plate. The electron deflects downwards and strikes the bottom plate. The magnitude of the electric field between the plates is 4.0 e+2 N/C. The separation of the...
  11. 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...
  12. H

    Coulomb's Law and Gauss's law

    Two electric charges q1 = 2 microC and q2 = -2 microC are located at \vec{r_1}=(1,0,0)m and \vec{r_2}=(0,0,-1)m respectively. Calculate the force on q1 in vector form. \vec{F_{12}} = \frac {1}{4\pi\epsilon_0}\frac{q_1q_2}{|\vec{r_1}-\vec{r_2}|^3}(\vec{r_1}-\vec{r_2}) is the formula I am...
  13. M

    Error in applying Coulomb's law

    Well, it's not so much an error as it is a fundamental lack of understanding about multiplication of units greater than vs less than 1. 1. If two charges are repelling each other which have values greater than 1, then the value of q1q2 will be greater than the individual values charge values of...
  14. M

    Magnitude, 2D co-ordinates and Coulomb's Law

    Homework Statement 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. (x1,y1) (x2,y2) (x3,y3) I know for definite I use the below calculation but...
  15. 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...
  16. A

    Coulomb's Law and point charges

    Two m = 6.0g point charges on 1.0-m-long threads repel each other after being charged to q = 120nC , as shown in the figure. What is the angle θ? You can assume that θ is a small angle. Hopefully the image will work. I feel like something is missing. I've gotten 7.4 and 3.4 degrees...
  17. N

    Applying Coulomb's law to HCl and LiF

    Homework Statement During a chem lesson my professor was demonstrating Coulomb's law using HCl. Fe = kq1q2/r^2 so what he did was he replaced q1 and q2 with 0.17 and -0.17. Then he showed an example with LiF and then replaced q1 and a2 with 1 and -1. I think he was trying to...
  18. E

    How Does Coulomb's Law Explain Forces and Fields Between Charges?

    q1= 2microC and q2=-4microC they are on a straight line 5.0 cm away from each other. a)find the magnitude of the net force on charge q2 due to q1 b) in what direction will the net force acting on charge q2 due to q1 be directed c)what is the magnitude and direction of the electric field...
  19. Greg Bernhardt

    Coulomb's Law: Definition & Summary

    Definition/Summary Coulomb's law is an inverse-square law stating that the force vector between two stationary charges is a constant times the unit vector between them and times the product of the magnitudes of the charges divided by the square of the distance between them: \mathbf{F}_{12}\...
  20. F

    Q) Deriving Gauss' Law from Coulomb's Law for a Single Point Charge

    Homework Statement Q) Use Coulomb’s Law to DERIVE the Gauss Law result for the particular case of A SINGLE POINT CHARGE. That is, using Coulomb’s Law, find the ELECTRIC FLUX going through a sphere of radius r surrounding one point charge of charge-magnitude q. THANK YOU Homework...
  21. B

    Changing Charge Distribution and Coulomb's Law

    Homework Statement Two small spheres of charge 10Q each separated by a distance d repel each other with a force F. In terms of F what would be the new repulsive force if 2Q were removed from one sphere and added to the other? Homework Equations F = kQq/r^2 The Attempt at a...
  22. Roodles01

    Coulomb's law three points on a line

    Homework Statement Three point charges, q1, q2 and q3 all on x-axis (i.e y=0 and z=0) +q1 at x = 0 -q2 at dist from origin x = a +q3 at dist from origin x = -2a where q1, q2 and q3 are magnitudes of the charges. Assuming q1 = q2 derive magnitude of q3 in order for there to be zero net force on...
  23. C

    Q vs q in Coulomb's Law: Understanding Notation for Charges

    Homework Statement This is a question about notation. When working with Coulomb's Law, is Q>0 and q<0? What is the difference between Q and q? Homework Equations n/a The Attempt at a Solution n/a
  24. Q

    Deriving Coulomb's law and other fundamental equations from F=ma?

    I saw a joke crib sheet for a physics class that said "F=ma, derive the rest," but is it actually possible to derive at least electricity and magnetism questions from Newton's second law?
  25. F

    Help using Coulomb's Law for a semi-infinite plane

    Alright, so I have tried my hand at this problem but keep hitting a wall. (NOTE: Every time I have tried to use ##\LaTeX## syntax in this post, it has not worked. As a result of this, and in the interest of making it easier for those who read this post to help me, I have attached a LaTex...
  26. B

    Coulomb's Law (3 charges in equilateral triangle)

    Three charged particles are placed at the corners of an equilateral triangle of side L = 1.74 m. The charges are q1 = 3.63 µC, q2 = −8.05 µC, and q3 = −6.31 µC. Calculate the magnitude and direction (counterclockwise from the positive x axis) of the net force on q1 due to the other two...
  27. Sneakatone

    Calculating Coulomb Forces Between Point Charges

    Homework Statement A point charge q1 = -3.9 μC is located at the origin of a co-ordinate system. Another point charge q2 = 7.3 μC is located along the x-axis at a distance x2 = 7.8 cm from q1. 1) What is F12,x, the value of the x-component of the force that q1 exerts on q2?Homework Equations...
  28. L

    Solving Coulomb's Law Homework Problem

    Homework Statement Having trouble with my vector addition when it comes to this homework question. Not really sure how to go about solving this problem since I'm new to coulomb's law problems and my prof didnt really give us many examples in class. Here is the picture of the charges. The...
  29. T

    Verifying Coulomb's Law: Q1, Q2 & R

    Hi, Can someone help me with this question? I understand Coulomb's law but i want to know if I am doing it right. So the charge of Q1= 2 mC Q2= 1 mC And R= 5 cm (0,05m) This is how i solved it. F= K(8,988x10^9) x (2x10^-6)x(1x10^-6) / (0,05m)^2 F= K(8,988x10^9) x 8x10^-10 F= 7.1904 N...
  30. N

    Coulomb's law in 3-D nightmare

    Homework Statement Charge q1 = 5 μC is at position ( 1 m; 2 m; -1 m) and a second charge q2 = -3 μC is in position ( -2 m; 1 m; 3 m). Find: a) The electrical force in vectorial form exerted on q1; b) The electrical field in vectorial form at the origin of the system (0; 0; 0); c) The electric...
  31. Avatrin

    Coulomb's law and spherical charge distribution

    Homework Statement Find the E produced by a spherical charge distribution with uniform charge density at a point inside the sphere, using triple integration. Homework Equations E = 1/4πε ∫f(x,y,z)/r^2 dV The Attempt at a Solution f(x,y,z) = p Radius of sphere = R Position of...
  32. PeteyCoco

    Electric Field over a charged cylinder using only Coulomb's Law

    Homework Statement What is the electric field at a point on the central axis of a solid, uniformly charged cylinder of radis R and length h? Homework Equations Well, I've set up the triple integral and have gotten to this point...
  33. K

    Monster E&M Question (Coulomb's Law, Electric Potential, Kinematics)

    Homework Statement A proton (charge +1e and mass 1.67e-27kg) and an alpha particle (charge +2e and mass 6.64e-27kg) are placed 3 fm (1 fm=10e-15m) apart. a)what is the force on each particle B)what is the potential energy of the system? c)what is the acceleration of each particle at the...
  34. Y

    Coulomb's Law And Electric Field between 2 Parallel Plates

    Homework Statement A uniform electric field exists in the region between two oppositely charged plane parallel plates. A proton is released from rest at the surface of the positively charged plate and strikes the surface of the opposite plate, 1.59cm distant from the first, in a time...
  35. V

    Coulomb's experiment (coulomb's law)

    Hello, I'm trying to imagine how Coulomb would've measured the force between electrically charged objects, but there are a few things I can't figure out. Is it true that Coulomb's law holds only for stationary charges? If it's true, then that very stipulation of the law would be violated...
  36. U

    Small clarification: applying Coulomb's Law

    Homework Statement Hi, I'm studying electric charges and fields, and I have a quick question about this example in my book: Everything is straightforward except the subscripts (13 and 23) on r in the denominators of initial Coulomb equations for F1 and F2. In the next step they just...
  37. G

    Coulomb's Law and Electric Force

    Homework Statement An object with a small mass (m) causes two balloons to float (neither ascending nor descending) in the air at a fixed distance from each other, as shown in the diagram. The balloons, with a volume (V) each carry a positive charge, Q. The balloons are said to be point...
  38. Y

    Does Coulomb's Law Apply Equally to Unequal Charges?

    Homework Statement Two point charges, q1 and q2, are separated by a distance r. If the absolute value of q1 < the absolute value of q2, then a) The magnitude of the electric force that q1 exerts on q2 is greater than the magnitude of the electric force that q2 exerts on q1. b) The magnitude...
  39. K

    What are point charges?Why we use point charges for coulomb's law?

    Homework Statement What is a point charge? and what is the purpose of it when the definition of coulomb's law says,"force b/w TWO POINT CHARGES is directly proportional to their magnitude,and inverse to the square of their distance..."...I mean what is the use of it,why only point charges...
  40. W

    Applying Coulomb's Law: Changes in Charge and Distance

    1. 1. Two charged spheres,10.0cm apart,attract each other with a force of magnitude 3.0 x 10^-6 N. What force results from each of the following changes, con- sidered separately? (a) Both charges are doubled, while the distance remains the same. (b) An uncharged,identical sphere istouched to one...
  41. A

    Gauss' Law for spherical shell vs Coulomb's law, regarding reativity

    Shalom We are used to hearing that Coulomb's law doesn't settle with the relativity principle that nothing moves faster than the speed of light, in the sense that it embeds 'Action in a Distance'. Meaning that if somthing changes in r1 at time t1, and we write the law for any t before...
  42. R

    Net force on a charge - Coulomb's law

    Homework Statement What is the force F on the 1 nC charge at the bottom? Figure: http://session.masteringphysics.com/problemAsset/1384340/5/pic1.jpg Homework Equations Coulomb's law - k*qq/r^2 The Attempt at a Solution 1) After splitting up the net force into their respective...
  43. B

    Coulomb's Law Electric Fields

    Homework Statement Two point charges are placed at the opposite corners of a rectangle as shown. What is the Electrical Field magnitude at each point due to the charges?Homework Equations Pythagorean theorem, E=kq/r^2The Attempt at a Solution r= square root of .8^2 +.4^2 =.89 E= 8.99x10^9 X...
  44. P

    Simple Coulomb's Law Question

    Simple Coulomb's Law Question Please Help! Homework Statement Two identical charged objects have charges of 6μC and -2μC. When placed a d distance apart, their forces of attraction is 2N. If the objects are touched together, then moved to a distance of separation of 2d, what will be the new...
  45. M

    Exploring Coulomb's Law: Electric Field & Potential Diff. of Spheres

    Homework Statement Constant in Coulomb's Law: k = 9 x 10^9 Nm^2/C^2 1) Two metal spheres are each given a charge as shown below. They are initially placed 30 cm from one another (center-to-center distance). (Qa = -6 x 10^-7 C) (Qb = -4 x 10^-7 C) (Ra = 5cm) (Rb=2cm). A) For purposes of...
  46. B

    Coulomb's Law involving triangle

    Homework Statement There are three point masses. 1 is fixed in space with the 2nd point mass directly below it on the ground. The 3rd point mass is an unknown distance to the right of mass number 2. These 3 point masses for a rt triangle with point 2 at the 90 degree angle. The vertical...
  47. R

    Coulomb's Law, what charge will make the two charges in static eq.

    Homework Statement In the figure below the charge in the middle is Q = -3.7 nC. For what charge q1 will charge q2 be in static equilibrium? Homework Equations F = (K*q1*q2)/(r^2)The Attempt at a Solution I'm not sure where to go after acknowledging that Fq1->q = -Fq2->q
  48. A

    Help electric charge Coulomb's law two charges?

    Homework Statement http://loncapa.vcu.edu/res/vcu/phys202/zzImages/two-charges-forces.bmp Problem#1: Two identical conducting balls, A and B, of identical masses m = 10 kg, are suspended in equilibrium by insulating massless strings in length L = 3 m. Both balls make the same angle θ = 30°...
  49. P

    Net Force Exerted by Two Charges on a Third Charge (Coulomb's Law)

    This problem has been posted before with different values for each variable and I did as best I could to complete it similarly. However, when I attempt to input my final answer I get it wrong every time. I just wanted to see where I am going wrong, thanks. Homework Statement Coulomb's law...
  50. S

    Question regarding Coulomb's Law

    Homework Statement Coulomb's Law tells us that a force will be acted upon charges which is dependent on the distance between the two charges. So if i have a negative charge on a rod and it is placed beside a neutral metal rod, how will the charges and the whole object experience force...
Back
Top