Coulomb's law Definition and 403 Threads

The title says it all--I'm working through The Feynman Lectures, and came across the assertion that a magnetic field can be thought of as a relativistic-transformation of an electric field (and vice-versa). This makes sense to me, since the magnetic field of a moving point-charge can easily be...

Homework Statement Provide a proof of Gauss’s law starting from Coulomb’s law for a point charge Homework Equations F=kq1.q2/r^2 (closed)s∫E.n.da=qenc/ε0 The Attempt at a Solution My starting point is: F21=1/(4∏.ε0).(q2.q1)/r21^2.r(unit vector)21 *Note, the 21 terms after...

Using Coulomb's Law, find the force between two objects that have charges of 5 Coulombs and 7 Coulombs, respectively. They are separated by a distance of 5 meters. For the same objects, one of which has a mass of 5kg and the other has a mass of 7kg, what is the force of gravity between them if...

Hi.I want to know why we multiply the separate charges in the coulomb equation.I understand that the force is proportional to the charges, but I don't understand why we multiply charges.Why just we don't add them together.Are there any theoretical explanation for this.The same goes for the...

Homework Statement What is the distance between two charges of -5.00 C each if the force of electrostatic repulsion acting on them is 4.00 x 10^3 N? q1 = -5.00 C q2 = -5.00 C Fe = 4.00 x 10^3 k = 8.99 x 10^9 Nm^2/C^2 Homework Equations Fe = kq1q2/r^2 The Attempt at a Solution...

Homework Statement Consider the arrangement of two point charges equal in magnitude but opposite sign (+Q, and -Q), which are a fixed distance d apart. Can you find a location where a third positive charge Q could be placed so that the net electric force on this charge is zero? Homework...

Homework Statement Two point charges are located on the y-axis as follows: charge q1=-2.5nC at y=-0.6m, and charge q2=+3.5nC at the origin. What is the net force (x, y components) exerted by these two charges on a third charge q3=+5.0nC located at y=-0.4m? Homework Equations F=k...

Homework Statement q1= 6.7 μC q2= -4.5 μC q3= 2.2 μC q4= 2.2 μC d= 7.7 cmWhat is the x-component of the net force on q1? Homework Equations The Attempt at a Solution This is part of an online problem set, and is currently the only question I have not answered correctly. I find it strange...

"K" in Coulomb's law Hi I want to ask how we can get k in Coulomb's law.

For calculating the force on a continuous charge distribution due to another continuous charge distribution, if F=kdqdq'/r^2 would you simply integrate first over dq' and then dq?

Homework Statement Homework Equations F=Keq1q2/r2 The Attempt at a Solution Using Coulomb's Law, here's what I've worked out: FAB=0.593N FAC=0.309N Fx=0.309 - 0.593cos60°= 0.0125 Fy=0.593sin60° =0.514 √(0.01252 + 0.5142) = 0.514 N/C and θ = tan-1(0.514/0.0125) = 88.6° I'm not sure why...

Homework Statement two charged particles held fixed in the xy plane are: q1= +3.0 μC, x1=3.5 cm, y1= 0.50 cm, and q2= -4.0 μC, x2= -2.0 cm, y2= 1.5 cm. (question 1) What is the magnitude and the direction of the electrostatic force on q2. ? (question 2) Where would a third charge q3= +4...

How correct is "deriving" Coulomb's Law from Gauss's Law Homework Statement Here is a question that appeared in my school question paper: "Derive Coulomb's Law from Gauss's Law." 2. The attempt at a solution I tried the following: Consider a Gaussian Sphere or radius $r$ By Gass's...

Homework Statement There are 3 charges q1,q2 & q3. Charge q1 is 1.67x10^-10 C and charge q2 is 9.13x10^-6 C. There is no net force on charge q3. x is the distance between q1 and q3 & (2-x) is the distance between q3 and q2. Distance between charge q1 and q2 is 2 meters. Find the distance x...

Homework Statement I should derive \vec{F_{q}} = \frac{-q'^{2}}{4∏ \epsilon_{0}} \frac{r'/a}{(r'^{2} - a^{2})} \hat{r} from \vec{F_{q''q'}} = k\frac{q' q''}{\left|\vec{x'} - \vec{x''}\right|^{2}} Homework Equations The Attempt at a Solution I know that q'' = -q'...

Hello dear Physics Forums members, My question is about the constant k, in Coulomb's law, which is: 1/4\pi ε0 Can anybody explain me where this constant comes from?

Homework Statement In the figure, particle 1 of charge 1.0 micro Coulombs and particle 2 of charge -3.0 micro Coulombs are held at a separation of L = 10.0 cm. If particle 3, of unknown charge is to be located such that the net electrostatic force on it is 0, what must its x and y...

I have an idea in which I need to manipulate a positron using an electrical field. However, in order for the problem to work, I need to make sure that the positron's kinetic energy is under 511 keV. to do this, I used Coulomb's law (F=\frac{kQ1Q2}{r^2}) to obtain the force. Because F = ma, I...

While studying electricity we always take point charges to calculate force between them according to coulomb's law.And to calculate the electric field around a point charge we take a test charge which is small. My question is: 1.What is the definition of point charge and test charge...

Hello everyone! As I understand it, Coulomb's Law gives the electrostatic force of attraction or repulsion between two point charges, in any single medium. |F| = \frac{Kq_1q_2}{r^{2}} And for any medium K is \frac{1}{4\pi\epsilon} My question is, how would different mediums in...

We were doing an experiment today and we had 2 aluminum foil balls hang next (but not touching) to each other. Both were initially grounded then we charged one of them while the other remained neutral. We observed an attraction between them but coulomb's law states that: F = k(q1*q2/r^2). If...

Homework Statement Three point charges, q₁= -5.00 μC, q₂= -4.00 μC, and q₃ which is negative are arranged as shown on three corner of side a=0.500 m. The direction of the forces on q₁ is at +20.0° with respect to the + x axis. Calculate the magnitude of q₃. The diagram looks something like...

Homework Statement SPH4U University Grade 12 Physics - Coulomb's Law? I have to determine the answer using Coulomb's Law. Please help me figure out how to do this ! Three point charges, q₁= -5.00 μC, q₂= -4.00 μC, and q₃ which is negative are arranged as shown on three corner of side...

Homework Statement (1) A point charge q1 = -2.9 μC is located at the origin of a co-ordinate system. Another point charge q2 = 5 μC is located along the x-axis at a distance x2 = 8.6 cm from q1. The answer to this was -17.64N. (2) Charge q2 is now displaced a distance y2 = 2.4 cm in the...

Homework Statement see attachment Homework Equations The Attempt at a Solution Do you see the step where they go from (1.35keq2)/a2 to 1.91keq2)/a2 ? I can't get that step. To my mind. If you square 1.35 then take its square root, you get 1.35 not 1.91

Homework Statement Two balls, each with a mass of 500 mg, are attached to the same point in the ceiling by strings with the length of 40 cm. The balls have been given equal and opposite charges, which caused them to separate in a way that the strings formed a 60-degree angle. Find the charges...

Homework Statement Two point charges of +30μC and -9μC are separated by a distance of 20.0 cm. What is the intensity of electric field E midway between these two charges? Homework Equations force electric= kQq/ r^2 Electric field= force elctric /q = k X Q / r^2 The Attempt at a...

Question: A baloon rubbed aginst denim gains a charge of -8microC. What is the electric force between the balloon and the denim when the two are separated by a distance of 5.0 cm? (Assume that the charges are located at a point.) Equations used: F electric = K q1 X q 2 / r^2 Steps...

Homework Statement The questions asks to consider the following comment about a situation where there are three point charges held fixed along a linear line. "There will be zero net electric force on the charge in the middle due to the other charges. Using Coulomb's law, the force due to...

I'm doing example 2.1 in Griffith's Electrodynamics book. Can someone explain where the cos(theta) comes from in the formula for dE? The formula is on the first image: Here.

I read an article on Coulomb's law which read, ''Coulomb's law only applies to point charges'' (or something along those lines). Am I wrong, or is there an equivalent that can work for magnets/big electric charges?

Homework Statement +2μC -2μC 0------------0 | | | | | | 0------------0 +2μC -2μC This is a square Each side in .2 (no units) Find the magnitude and direction of the electric field at the center of the square...

Homework Statement How does … (a) the electrostatic force exerted by a proton on an electron compare to the electrostatic force exerted by an electron on a proton? (b) the gravitational force exerted by a proton on an electron compare to the gravitational force exerted by an electron on a...

Is this question worded poorly or is it just me? Three charges are on the y-axis. Charges -q are at y = ±d and charge + 2q is at y = 0. (a) Determine the electric field E along the x-axis. (b) Verify that your answers to part a has the expected behavior as x becomes very small and very...

Homework Statement In the figure, the net electrostatic force on charge Q2 is zero. If Q1 = -5 nC and Q2 = +7 nC, determine the magnitude of Q0. http://www.webassign.net/bauerphys1/21-p-079-alt.gif Homework Equations F = (k*q1*q2)/d^2 The Attempt at a Solution I notice that Fnetx...

Homework Statement In a region of two-dimensional space, there are three fixed charges: +1 mC at (0, 0), -2 mC at (16 mm, -6 mm), and +3 mC at (-6 mm, 20 mm). What is the net force on the -2-mC charge? -magnitude -direction (° counterclockwise from the +x-axis) Homework Equations F =...

Homework Statement Three positive particles of equal charge, +11.5 µC, are located at the corners of an equilateral triangle of side d = 13.0 cm (Fig. 16-50). Calculate the magnitude and direction of the net force on each particle. Image is here...

Problem: a charge +Q is located at the origin and a second charge, +4Q is at a distance d on the x-axis. where should a third charge, q, be placed, and what should be its sign and magnitude, so that all three charges will be in equilibrium. attempt: I don't know how to solve it fully, but...

Homework Statement Two small pith balls, each of mass m = 12 g, are suspended by 1.2 m fine (so that we can neglect their mass in this problem) strings and are not moving. If the angle that each string makes with the vertical is θ = 42.6°, and the charges on the two balls are equal, what is...

Homework Statement One charge of (+5µC) is placed in the air at exactly x = 0, and a second charge (+7µC) at x = 100cm. where can the third charge be placed so as to experience zero net force due to the other charges? Homework Equations F=KQ1Q2 / D^2 The Attempt at a Solution Q1 =...

Homework Statement We know that the magnitudes of the negative charge on the electron and the positive charge on the proton are equal. Suppose, however, that these magnitudes differ from each other by 0.00094%. With what force would two copper coins, placed 1.1 m apart, repel each other...

Homework Statement Two very small 8.55-g spheres, 15.0 cm apart from centre to centre, are charged by adding equal numbers of electrons to each of them. Disregarding all other forces, how many electrons would you have to add to each sphere so that the two spheres will accelerate at 25.0g when...

Homework Statement Revered members, Please see my both attachments. Homework Equations F21 = (q1q2/4∏ε0r122)*r12cap(unit vector) Is it wrong to use r12 instead of r21 for F21. Because my second attachment uses r21 for F21 and r12 or F12. I am confused. Please help which is correct...

Why use k = 1/[4(pi)(epislon)] and epsilon = 8.8 * 10^(-12) and subsequently, k = 9 * 10^9 It could simply be k = 9 * 10^9, and different k for different medium instead of different permittivity for different medium. What I mean is why does Pi, (I can handle the 4) comes into the...

The idea being that I have two particles of opposite charge (particles implying the mass is negligible relative to the electric forces at play). One is fixed at the center, the other orbits around at a fixed radius. How would I go about solving for the angular velocity required to keep this...

I'm having a bunch of trouble with an electrostatics questions as well as an electric fields question. I'll start with the electrostatics problem. Homework Statement I am given the following equilateral triangle and asked to calculate the net electrostatic force on each charge...

Homework Statement http://i.imgur.com/ITrJq.png Homework Equations F=kq1q2/r^2 (Coulomb's Law) The Attempt at a SolutionWhenever I try to get the answer, I keep coming up with 15.47cm. I found the Coulomb's law for the third particle in relation to the other two, then set those equations...

Homework Statement three objects carrying charges of (a)-4x10^-6 C, (B)-6x10^-6 C, and (c)+9x10^-6 C are placed in a line equally spaced from left to right by a distance of 0.5m. calculate the magnitude and direction of the net force acting on each. Homework Equations Force of the magnitude...

Question: Of the charge Q initially on a tiny sphere, a portion q is to be transferred to a second, nearby sphere. Both spheres can be treated a particles. For what value of q/Q>0.5 will the electrostatic force between the two parts have 1/5 of the maximum possible value? Attempt: F = [...

A 5C point charge located at (2m, 3m, 4m) and a 6C point charge located at (4m, 3m, 2m) together exert a net force on a 7C point charge located at (2m, 4m, 3m) is most closely represented by... (a) k(-6i + 15j - 10k) N (b) k(-8i + 13j - 12k) N (c) k(7i + 14j - 11k) N (d) k(7i - 14j - 11k)...