# What is Coulombs: Definition and 115 Discussions

The coulomb (symbol: C) is the International System of Units (SI) unit of electric charge. Under the 2019 redefinition of the SI base units, which took effect on 20 May 2019, the coulomb is exactly 1/(1.602176634×10−19) elementary charges. The same number of electrons has the same magnitude but opposite sign of charge, that is, a charge of −1 C.

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1. ### 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. ### Coulomb's Law: Solving Problems with Electric Charges

This is my attempt but they said my answer is wrong
3. ### What is the maximum charge in Coulombs can be obtained in ionistor?

What is the maximum charge in coulombs can be obtained on the plates of ionistors like these: https://en.wikipedia.org/wiki/Supercapacitor ?
4. ### Need a machine to impart measurable charge (Coulombs) at will

Hi there, Does anyone know of a machine/equipment/technology, etc. that allows a person to give charges (Coulombs) to conductors in a measurable way? I've rubbed a ton of plastic rods with fur but that's not too measurable. The Van De Graaff is overkill or it if I try to connect alligator clips...
5. ### Magnetic field of a moving charge and coulombs force

By relativity+coulombs force, I worked out that the (magnitude of the) magnetic field of a charge Q moving at speed V should be (ϒVV/c2)Q/(4πε0r2) or in terms of mu, ϒVμ0VQ/(4πr2) (where the distance r is measured normal to V). When I google the answer I only find the same thing but without the...
6. ### Work, energy, power unit (coulombs)

Homework Statement For a positively-charged particle at the origin, and a negatively-charged particle lying to its right on the positive x-axis, the electrostatic force on the negative charge is attractive, and Coulomb's Law gives the magnitude of that force: F = k |Q1| |Q2| / x^2 k is...
7. ### Possible variables for Coulombs Law?

COULOMBS LAW F= K Q1 Q2 / R2 How would I solve for Q1 and Q2?
8. ### 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
9. ### 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
10. ### 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...
11. ### Calculating Electrical Force on Alpha Particle Near Gold Nucleus

Homework Statement An alpha particle (charge equals +2e) is sent at high speed toward a gold nucleus (charge equals +79e). What is the electrical force acting on the alpha particle when it is (2.0 x 10-14) m from the gold nucleus? Homework Equations I tried using Coulomb's law, which is E =...
12. ### Find the magnitude of the current density

Homework Statement A beam contains 3.95×108 doubly charged positive ions per cubic centimeter, all of which are moving north with a speed of 1.64×105 m/s. What is the magnitude of the current density? Homework Equations J = nev n = electron density e = electron charge v = drift velocity The...
13. ### How Many coulombs pass through each resistor in a circuit?

Homework Statement My question relating to physics and electric circuits, is "If a circuit consists of a 12 volt battery and two ohm resistors connected in series, then how many Coulombs pass through each resistor in a second". Thank you all so very much. Homework Equations V=IR The Attempt...
14. ### What would the final charge on the rod be?

I had a question. If a glass rod, with a charge of 5.4x108 C touched another insulator so that all of the excess electrons are shared equally. What would the final charge on the rod be? I don't understand how to reach the answer of 2.7 x108 C. Thanks in advance. :)
15. ### Converting Coulombs to Joules Without Voltage

Hi Is it possible to convert coulomb to joule without knowing volt?
16. ### What is the charge (Coulombs) of a nanogram of electrons?

Homework Statement What is the charge of a nanogram of electrons? This was a test question for me. I didn't know the exact definition of a coulomb, so I guessed about 1. something C. The options were 1.something C, 0.03C, or like 3.64C. Someone care to explain/help? thanks Homework...
17. ### Why is the basic charge not equal to the reciprocal of a Coulomb?

why isn't the number of e or p making a Coulomb the same as the reciprocal of the 'basic' charge if the basic charge is defined as a fraction of a Coulomb? basic charge = 1.6 x e-19C, but number of p or e constituting a C is 6.25 x e18
18. ### 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...
19. ### MHB Webpage title: Calculating Coulombs in a Nickel Coin

How many Coulombs of charge positive and negative are there is a coin of 5 g of mass? Answe: 2,3.105 C I don't know but I have no idea I think there is no enough data
20. ### 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...
21. ### 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
22. ### Charge and Coulombs - what does 0 coulombs mean?

I'm studying electrostatics and magnetism right now in Physics II for Engineers. I'm doing ok with most of the concepts, doing well in class, etc. I'm missing (or at least not 100% sure) of a basic part of the concept here. I feel like I'm correct in assuming that an object with no charge is...
23. ### 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...
24. ### 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...
25. ### 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 =...
26. ### 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...
27. ### Coulombs force law in a three dimensional coordinate system problem

Two point charges of Q1 = +37 nC and Q2 = +70 nC are located at points (1,3,0) m and (0,0,2) m, respectively. Q : Calculate the force exerted on Q2 by Q1. Attempt : I applied phythagoras theorem to find the distance between Q1 and Q2, I then applied coulombs force law equation directly...
28. ### 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...
29. ### Finding attractive force between two ions, using Coulombs equation

Homework Statement "Calculate the force of attraction between a K + and an O 2- ion whose centers are separated by a distance of 1.5 nm." Homework Equations F = [ k (Z1)(Z2) ] / r^2 The Attempt at a Solution Both valences are filled when K is a + charge and O is a 2-...
30. ### 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 *...
31. ### 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...
32. ### 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...
33. ### 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...
34. ### 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...
35. ### Charge of an electron in Coulombs?

Is it correct that the charge of an electron in Coulombs is - 1,602 176 565(35) • 10-19 C ? By inserting this in the formula for current I = Q / t, that would make the current a negative number. I don't reckon having read about negative currents though. So what's the explanation for how...
36. ### 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
37. ### How Do Coulombs and Amperes Measure Electricity?

What is exactly one Coulomb? Wikipedia says "One coulomb is the magnitude (absolute value) of electrical charge in 6.24150965(16)×10^18 protons or electrons." It also says " It is defined as the charge transported by a steady current of one ampere in one second" But also 1 proton has a charge...
38. ### Understanding Coulomb's Constant: Explained for Beginners

Hi This may sound like a trivial question, but I'm a beginner physics student and need some help understanding what the k constant is from Coloumb law. F_e = k_e\frac{k_1 k_1}{r^2} where k_e = \frac{1}{4\piε_0} I did read a bit about it and I have two questions...
39. ### What is the magnitude of each fixed charge in coulombs?

Homework Statement Four point charges, q, are fixed to the four corners of a square that is 13.1 cm on a side. An electron is suspended above a point at which its weight is balanced by the electrostatic force due to the four point charges, at a distance of 20 nm above the center of the square...
40. ### 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. ### 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. ### 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. ### 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. ### How Many Coulombs Can Flow Through a 15A Breaker Before It Trips?

Homework Statement Given a 15A breaker, what is the max number of coulombs that can flow through before the breaker trips? Homework Equations i = dq/dt A = C/s The Attempt at a Solution No time value is given so I can't integrate dq = i dt from any limits. Is the right thing...
45. ### 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...
46. ### 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...
47. ### 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 =...
48. ### 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...
49. ### 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!
50. ### 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...