Point charges Definition and 359 Threads

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 A point charge −3 pC is concentric with two spherical conducting thick shells, as show in the figure below. The smaller spherical conducting shell has a net charge of 22 pC and the larger spherical conducting shell has a net charge of 18 pC. 1-4)Answer in units of...

Homework Statement A -2 μC charge and a 10μC charge are separated by 15.0cm. At what point is the electric field zero? At what point is the electric potential zero? Homework Equations E=(kq1/r1^2)+(kq2/r2^2) V=kq1/r1 + kq2/r2 The Attempt at a Solution My main problem is with...

Homework Statement Two point charges Q and -Q are separated by a distance d. The point p forms an equilateral triangle with the two charges of side length d. Find the magnitude and direction of the electric field at point p. What is the electric potential at P? Then, a charge of 2Q is placed...

Hey all, I am using the Joukowski transform to calculate the electrostatic potential and streamlines around an elliptical cylinder. The flow is caused by two point charges (one positive, one negative). My idea was, of course, to first solve the problem for a circular cylinder, and then...

Three negative point charges lie along a line as shown in the figure. figure: http://tinyurl.com/7xppvc8 Find the magnitude and direction of the electric field this combination of charges produces at point , which lies 6.00 from the charge measured perpendicular to the line connecting the...

Homework Statement Two point charges, 3q and q lie along x-axes. 3q is at 0.00 m and q is at 3.0m. Find the point between the 2 charges at which the net force on charge q is zero. Homework Equations F=kq1q2/r^2 The Attempt at a Solution Really can't figure this one out. Missed the...

Homework Statement The figure shows five point charges placed on a line, at intervals of 1 cm. For what values of q1 and q2resultant electrical force exerted on each of the three charges is zero? Homework Equations I imagine the law of coulomb is used here, however, I'm not sure how I'm...

Homework Statement Three point charges lie along a circle of radius r at angles of 30°, 150°, and 270° as shown in the figure below. Find a symbolic expression for the resultant electric field at the center of the circle. Homework Equations \vec{E}=\frac{k_{e}q}{r^{2}} The Attempt at a...

The result I got seemed sort of messy and I'm not sure I've gotten the basic idea correctly, so I thought I'd make it sure. I think this was the easiest problem we had to solve for charge distributions and point charges and whatnot, so I know for sure I'll have to practice more if I made any big...

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 =...

In many articles authors describe FMM for particles. e.g. http://www.csci.psu.edu/seminars/fallnotes/fmm.pdf http://www.umiacs.umd.edu/labs/cvl/pirl/vikas/publications/FMM_tutorial.pdf In other articles authors describe FMM for charged surface. How does these formulations relates? Main...

In lecture 2 of http://oyc.yale.edu/physics/physics/fundamentals-of-physics-ii/content/class-sessions , around the 50 minute mark, the professor calculates the value of an electric field at a point (x,0,0) on the x-axis of a cartesian coordinate system. (The video can be rather slow loading, so...

Homework Statement There are three point charges, q1 has a magnitude of 3.00mC (the sign is not known) and is 5.0cm away from P and 13.0 cm away from q2. P is 12.0cm away from q2 and the three points form a triangle. The net electric field at point P is entirely in the negative y-direction...

Homework Statement Two point charges q1 and q2 are located on a straight line normal to a grounded (V=0) conducting plane. Choosing the z axis to go through the charges, q1 is at a distance z1 above the conductor, and q2 is at a distance z2. Find the potential V(x,y,z) everywhere above...

Today I was reflecting about the statement that increasing the distance between two large charged plates increases voltage, when I started to wonder what the behavior was near point charges (more voltage? as much? less?). Q and -Q are charges. P1 and P2 are locations. Q @ x=0m P1 @ x=1m...

My physics textbook defines the electric potential energy of a system to be equal to the external work that must be done to assemble the system, bringing each charge in from an infinite distance. And then it goes on the explain an example: "Figure 24-15 shows two point charges q1 and q2...

Homework Statement Consider two point charges a distance 1.5 cm apart. These charges have an electric potential energy of -190 micro J. The total charge of the system (the sum of the two charges) is 26 nC. What is the charge of each point charge? Homework Equations Uelec = K*q1*q2/d...

Homework Statement The questions are based off of the diagram I attached. First, I had to find the strength of the electric field due to each charge at (0 cm, 8 cm). Now I need to find the total electric field (both magnitude and direction) at (0 cm, 8 cm) and the total electric potential...

Homework Statement Consider three charges arranged as shown. + + - 1 2 3 What is the magnitude of the electric field strength at a point 1.5 cm to the left of the middle charge? The value of the Coulomb constant is 8.98755 × 10^9N
m2/C2. Answer in units of N/C q1=8.2 µC= 8.2*10^-6...

Four identical point charges of q = 8.37 nC are at the four corners of a square with a side length of 11.2 cm as shown in the figure. (had to make it but same thing since I can't copy it) q q Q q q Edit: doesn't come out right when I post so imagen a square little q's on...

Homework Statement Three point charges are located at the vertices of an equilateral triangle. The charge at the top vertex of the triangle is -4.4 µC. The two charges q at the bottom vertices of the triangle are equal. A fourth charge 2 µC is placed below the triangle on its symmetryaxis, and...

Homework Statement (a) Find the magnitude and direction of the net electrostatic force exerted on the point charge q3 in the figure below. Let q = +1.5 µC and d = 27 cm. http://www.webassign.net/walker/19-31.gif Homework Equations The Attempt at a Solution I found Fx = 1.7 N...

point charges in an electric field Homework Statement Problem: A +8.75 micro C point charge is glued to a frictionless table. It is tied to -6.5 micro C point charge by a 2.5 cm string (weightless and nonconducting). A uniform electric field of magnitude 1.85*10^8 N/C is directed parallel to...

Hi! I am having a tough time with this question, and would just like some clarification if that's at all possible! I feel I may just be missing a key concept, however, any help is appreciated! Thanks. Homework Statement Point x is .25 m away from a point charge of +4.7*10^-8 C, point Y is...

Homework Statement Three equal positive point charge of magnitude Q=7.00uC are located at three corners of a square of edge length d=4.8cm. A negative charge of -21.00uC is placed on the fourth corner. A) At the position of the negative charge, what is the magnitude of the electric field due...

Homework Statement http://www.ridemtl.com Homework Equations F = k(q1q2/r^2)The Attempt at a Solution I know pretty much what to do for the problem, but I cannot get the right answer. I think my issue lies within what angles I am using for the components. Because it is an equilateral triangle...

Homework Statement Two point charges q1 = 2\muC and q2 = -2\muC are placed at r1 = (3,0,0) m and r2 = (0,0,4)m respectively i) What is the force of q1 (in vector form)? ii) What is the electric field at the origin? iii) What is the electric dipole moment of this arrangement (in vector...

Homework Statement Point charges +q and -q are placed at +50 cm and -50 cm on the x-axis, respectively. Is the electric field at the origin (halfway between the charges) zero or nonzero? If nonzero, which direction does it point? Homework Equations The Attempt at a Solution Well...

What is a point charge? I have read wikipedia but m not much satisfied... please can you explain me in your own words? thanks

Hi everyone, I got a little question. Let's say we have 3 point charges on a line, for example on the x axis. 1----2----3 something like this. If I want to calculate the Force on point charge one, why am I allowed to just add the forces 12 and 13. I saw it in a book and was confused...

Homework Statement Four point charges have equal magnitudes. three are positive and one is negative, as the diagram shows. they are fixed in place on the same straight line, and adjacent charges are equally separated by a distance d. consider the net electrostatic force acting on each...

I'm trying to get a deeper understanding of how two particles such as protons interact with each other. In high school physics, I was told that they give off a field, which is felt by the charges, and then repels them. My first question is, if I fire two protons at each other head on (lets...

Homework Statement "Two point charges 2.0cm apart have an electric potential energy -180 microJoules. The total charge is 31 nC. What are the two charges?" Homework Equations V= k * q / r The Attempt at a Solution I understand that V = -180 * 10^-6, k = 9*10^9, r = 0.02m, and the...

Homework Statement Two positive point charges are 4.60 cm apart. If the electric potential energy is 75.0 x 10^-6 J, what is the magnitude of the force between the two charges? Homework Equations U=kq/r (1) F=kqq/r^2 (2) The Attempt at a Solution So I tried using (1)...

Homework Statement I am looking to demonstrate that the expressions for the charge and current density of point charges satisfy the equation of continuity of charge. Intuitively it makes sense to me but I run into trouble with the delta function when I try to prove it mathematically.Homework...

Two point charges are located on the x axis: one charge q_1 = -15.0nC located at x_1 = -1.745m , and a second charge q_2 = 38.5nC at the origin.What is the total force along the x axis, including sign, exerted by these two charges on a third charge q_3 = 47.0nC placed between q_1 and q_2 at x_3...

Homework Statement Determine the resultant force acting on a point charge of -2 x 10 ^-6 C situated at the origin of a rectangular coordinate system in the vicinity of point charges 3x10^-6 C and -4x10^-6 C at distances 0.12 m along the positive x-axis and 0.08m along the half-line x=y...

1. Homework Statement An infinite number of point positive charges of 2.0 C each are arranged in the following linear configuration with a = 88 cm. Find the electric potential at the point 0 on the scale. (link to image) http://img232.imageshack.us/i/prob02.gif/ 2. Homework...

Homework Statement An infinite number of point positive charges of 2.0 C each are arranged in the following linear configuration with a = 88 cm. Find the electric potential at the point 0 on the scale. (link to image) http://img232.imageshack.us/i/prob02.gif/...

Homework Statement Two point charges qA and qB are located on the x-axis at x=a and x=b. The figure is a graph of Ex, the x-component of the electric field. What are the signs of qA and qB? Homework Equations http://session.masteringphysics.com/problemAsset/1071455/4/29.EX31.jpg...

https://wug-s.physics.uiuc.edu/cgi/courses/shell/common/showme.pl?cc/DuPage/phys2112/spring/homework/Ch-24-E-Potential/2_pt_chrgs/set3p02.gif" 1. Homework Statement Two positive charges, each with Q = +11 µC, are fixed to the x-axis at x = +a and x = -a, where a = 2 m. (a) Find the electric...

Homework Statement A ring of charge with radius R = 0.5 m is centered on the origin in the x-y plane. A positive point charge is located at the following coordinates: x = 19.0 m y = -14.6 m z = -2.6 m The point charge and the total charge on the ring are the same, Q = +40 C...

Homework Statement Two large parallel copper plates are 5.0cm apart and have a uniform electric field between them. An electron is released from the negative plate at the same time that a proton is released is released from the positive plate. neglect the force the particles have on each other...

Homework Statement A point charge of -7e-6 C is located at x = 3 m, y = -2 m. A second point charge of 12e-6 C is located at x = 1 m, y = 3 m. Homework Equations The Attempt at a Solution Dq1 = sqrt(20) Dq2 = sqrt (13) E1 + E2= k(-7e-6)/20 + k(-7e-6)/20 = 11444.96 N/C...

Homework Statement The attractive electrostatic force between the point charges 8.12×10−6C and Q has a magnitude of 0.670N when the separation between the charges is 7.26m. Find the sign and magnitude of the charge Q. (this is a direct cut and paste) Homework Equations...

Hello, I'm having a little trouble with this: Coulomb Force Point Charges on Cube Homework Statement Identical charges of Q (C) are located at the eight corners of a cube with side L (m). Show that the coulomb force on each charge has magnitude: 3.29Q^2/4\pi\epsilon_0l^2 Homework Equations...

Homework Statement Point charges of 12x10-6, -7x10-6 and 4x10-6 are located at (2,0,-1), (1,1,2) and (2,-1,2). a. Determine D(flux density) and E(electric field strength) at (1, -1, 3). b. What is the flux passing through the sphere of radius of 2.5 centered on the origin Homework...

Homework Statement A 4microC point charge is placed at the coordinate origin. Two other point charges are placed on the x axis: q1 at x=30cm and q2 at x=50cm. Find the magnitude and sign of q1 and q2 if the net force on each of the three charges is zero. Homework Equations...

Homework Statement Two point charges are placed on the x axis: +5 microC charge at x=0 and +8 microC charge at x=0.9m. Where on the x-axis can a third charge be placed so that the net charge on all three charges is zero? Determine the magnitude of the third charge. Homework Equations...