Point charges Definition and 359 Threads

How to find potential ENERGY between two point charges?I know how to find potential difference between two points and I also know how to find potential at any point . potential difference between two points 1 and 2 is simply ##V1##-##V2## potential at any point r=V While source charge is Q...

Homework Statement Four equal point charges q = +22.4 μC sit at each corner of a square. What charge Q, in μC, must be placed in the center so all the charges are in equilibrium? Your answer must include the sign of the charge. Homework Equations F = q1*q2 * k / r^2 3. The Attempt at a...

Homework Statement Two points charges. q1=2.4e-6 C is located at (0,0) q2=-5.7e-6 C is located at (3,0) I must calculate the magnitude of the Electric field at (0,0) Homework Equations E=kq/r^2 ; k=9e9 The Attempt at a Solution The electric field at (0,0) due to q2=9e9x(-5.7e-6)/3^2 =...

Earnshaw's theorem http://en.wikipedia.org/wiki/Earnshaw's_theorem gives a straightforward reason why we can't have a static equilibrium for a system of point charges. For some time I've been trying to find out if anyone's worked out a similar proof for the impossibility of a dynamic...

1. How far apart must two point charges of 75.0 nC be to have a force of 1.00 N between them?Homework Equations F = k Q1Q2/r2[/B]3. 1N = 9e10 * 75e-10 squared/r squared r2= 9e10 * 75e-10 squared/1N r2= 9*75*75e-10 r2= 5.0625e-7 r= square root of 5.0625 * square...

I'm studying for the physics GRE and am fairly poor with EM. 1. Homework Statement What is the work needed to assemble four point charges q into a regular tetrahedron of side length a? Homework Equations W = 1/2ΣqiV(ri) The Attempt at a Solution Assume that the origin is at one of the...

Hey guys, new to this forum. Currently studying a mechanical engineering degree (first year), but I'm having real problems with some of the electrical side of it, mainly electric fields. Any tips or help on how to answer these two questions: 1. Two point charges of +3.1 muC are separated by a...

Homework Statement It is the last part, part (c) that I'm having trouble with, but I'll post the entire question for clarity. Three charges (q) form the vertices of an equilateral triangle. A fourth charge Q ( Q = -q ) is placed at the center of the triangle. (a) will the charges at the...

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...

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...

Homework Statement What is the potential energy of the system composed of the three charges q1, q3, and q4, when q1 is at point R? Define the potential energy to be zero at infinity. Charges are arranged in a triangle, with q3 and q4 located up and down 2.2 cm from the origin, and q1 on the...

Homework Statement A point charge q =+6.4 \mu \mathrm{C} is placed at each corner of an equilateral triangle with sides 0.29 \mathrm{m} in length. What is the magnitude of the electric field at the midpoint of any of the three sides of the triangle? Hint: if you are careful to examine the...

Homework Statement Two point charges q1 = 4.90×10-5 C and q2 = 2.45×10-4 C are separated by a distance d = 0.10 m. Compute their net electric field E (x) as a function of x for the following positive and negative values of x, taking E to be positive when the vector E points to the right and...

Homework Statement Find the Electrostatic potential energy of a cubical configuration of point charges. (One charge on each corner of a cube). Each of the charges is 3.00e and the edge of the cube is 3 cm. Homework Equations U = kqQ/r The Attempt at a Solution I'm pretty sure I understand...

Homework Statement In the figure, three point charges are arranged in a equilateral triangle of side a= 1.40×10-2 m. Sketch the field lines due to + Q and -Q, where Q = 2.50×10-5 C , and from them determine the direction of the force that acts on +q = 5.00×10-8 C because of the presence of the...

Homework Statement In the figure, two point charges q1 = 3.40×10-5 C and q2 = 1.70×10-4 C are separated by a distance d = 0.10 m. Compute their net electric field E (x) as a function of x for the following positive and negative values of x, taking E to be positive when the vector E points to...

Homework Statement How can I find the nuetral point between two charges or more ? Example:[/B] (-Q3)...(0.8m)......(Q2)...(0.3m)...(P)...(0.3m)...(Q1) Q1=2nC ,,, Q2=3nC,,, Q3=-4C ,,, q: Determine in which direction must be Q3 moved to make P neutral? Calculate the distance which P will be...

First by "stationary" I mean "with respect to each other" so as to avoid introducing relativity problems. I'm wondering whether there's a way to prove or disprove that given N > 1 point charges q_1, q_2, ..., q_n, is there always a way of putting them in 3-dimensional space such that all of...

Homework Statement A point charge $$q_1=+20\cdot 10^{-9}[Coulomb]$$ is 5[cm] distance from charge $$q_2=-12\cdot 10^{-9}[Coulomb]$$. An electron is released from 1[cm] distance from q2. what is it's velocity 1[cm] from q1. Homework Equations The potential=Voltage from a point charge...

Homework Statement Use either image charge method of separation of variables to solve: The distance between two large, grounded parallel conducting plates is 4x. Between them, two point charges +Q and -Q are inserted and have a distance x and 3x from one of the plates. (A line connecting the...

Homework Statement Two point charges of equal value are placed a distance 2b from one another. In the middle, there is a grounded conducting sphere. What is the minimum radius of the sphere required to cancel out the repelling force between the two charges? (Solve using Image Charge Method)...

Homework Statement [/B] The following is on a practice exam I have been completing. In advance, it is part b I am struggling with. Two point charges Q1 = +5*10^(-6)C and -2*10^(-6)C are 50cm apart. a) Where along a line that passes through the two charges is the electric potential zero (apart...

Homework Statement Find electric field anywhere on the x-axis due two two point charges Q at (0,0,d) -Q at (0,0,-d) Homework EquationsThe Attempt at a Solution AttachedSomehow I am not getting the correct answer. I reviewed my steps with 4 people and we could not find the error! I'm...

HI, Would the voltage change between two point charges say + and - as you increase the distance between them? When you have two charge parallel plate capacitors, that was charged but a battery then disconnected, its a different story right? The voltage increases? Thanks

Homework Statement There is a −3 µC point charge at (0,0,4) and a +3 µC point charge at (0,0,-4). What is the magnitude and direction of the electric field at point (0,0,8)? What is the magnitude and direction of the electric field at point (0,0,8)? [/B] Homework Equations E = \frac{ k_e q...

Two positive charges Q1 and Q2 are separated by a distance d. Find a general expression for the distance from Q1 at which the electric field is 0 by defining Q2 as alphaQ1 (alpha > 0 with alpha not equal to 1). This expression should contain alpha, d, and possible some numeric constants. Check...

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...

The basic equation is as follows: U=∑kqiqj/Rj with (i≠j) My question is how is this definition useful? What makes you want to say that is the potential energy of the system? For example, I thought that it is useful because if all particles change in position then you could evaluate that...

Homework Statement Two positive point charges, ##q_A## and ##q_B## (masses ##m_A## and ##m_B##) are at rest, held together by a massless string of length ##a##. Now the string is cut, and the particles fly off in opposite directions. How fast is each one going, when they are far apart? [from...

Homework Statement Hi! This is not really a problem. I'm just confused on how to express the charge distribution of a set of point charges in spherical coordinates. From our discussion, ρ(\vec{r})=\sum\limits_{i=1}^N q_i δ(\vec{r}-\vec{r}') where \vec{r} is the position of the point where...

Homework Statement Find the magnitude of the electric field this comination of charges produces at point P, which lies 6.00cm from the -2.00μC charge measured perpendicular to the line connecting the three charges. Homework Equations E=k\frac{Q}{r^{2}} F=k\frac{q_{1}q_{2}}{r^{2}}...

Homework Statement We have three point charges Q_1, Q_2, Q_3 , forming together an isosceles triangle. Two sides are of equal length r . The point charge Q_1 is located at (0,0), the point charge Q_2 is located at (x_2,0) and The point charge Q_3 is located at (\frac{x_2}{2},\sqrt{r^2 -...

Homework Statement Two point charges (q1 = -2.6uC and q2 = 8.6uC) are fixed along the x-axis, separated by a distance d = 9.7cm. Point P is located at (x,y) = (d,d) 1. What is Ex(P), the x-component of the electric field produced by q1 and q2 at point P? 2. What is Ey(P), the value of the...

Question: Two positive charges q(a) and q(b) and masses m(a) and m(b) are at rest, held together by a massless string of length d. Now the string is cut, and the particles fly off in opposite directions. How fast are each going when they are far apart.My attempt: From this the first thing I...

Consider the following charge distribution:A positive charge of magnitude Q is at the origin and there is a charge -Q on each of the x,y and z axes a distance d from the origin. I want to expand the potential of this charge distribution using spherical coordinates.Here's how I did it...

Homework Statement Three point charges are located in an equilateral triangle with side 0.330 cm, where q1 = +8.30 µC, q2 = −8.20 µC, and q3 = +1.90 nC. A) What is the electric field at the location of q3? Enter the x component, then the y component. B) What is the force on q3? Enter the x...

I'm a little confused about something that came up in a lecture a while back. There's nothing about it any books or online seemingly... The energy for bringing four point charges from infinity to a their relative positions was calculated. This was done by saying the work to bring in the first...

Homework Statement A point charge q2 = -4.5 μC is fixed at the origin of a co-ordinate system as shown. Another point charge q1 = 3.6 μC is is initially located at point P, a distance d1 = 7.3 cm from the origin along the x-axis 2) The charge q2 is now replaced by two charges q3 and q4...

The surface photovoltage effect suggests that the potential at the surface of a semiconductor will change when it is illuminated since hole-electron pairs are created. The regions near the surface (depletion regions) contains defects that create a built-in voltage and built-in potential and...

Homework Statement A charge + q is fixed at each of the two points (±a,0,0). Show that the potential V at a point (x,y,z) near to the origin may be expressed as V = [q/4∏*ε*a] [[2+(2x2-y2-z2)/a2] where x, y and z are small compared with a. Homework Equations V(x) = q/4∏i*ε*r ...

Homework Statement Both Q1 = Q2 = +5E-6 and are harnessed to screen and in a vacuum.----Q1---A----Q2------B--------P this is x axis, A and B are distances Homework Equations kQ/r^2 The Attempt at a Solution So the E field at point P is KQ1/(A+B)^2 + KQ2/(B)^2 My question is Why...

Homework Statement Two points are resting on a string. The first point is resting at x = 6.0 m and has charge q1 =−7.1 µC. The second point is resting at x = −4.0 m and has charge q2 = −4.3 µC. At what location is the total electric field zero from the two points(other than infinity)...

Two point charges are placed on the x-axis as follows: charge q1 = 4.01nC is located at x= 0.201m , and charge q2 = 5.00nC is at x= -0.301m. What is the magnitude of the total force exerted by these two charges on a negative point charge q3 = -6.03nC that is placed at the origin? I know I...

1. 1: Suppose eight identical point charges q are placed at the corners of a cube with side length L. Find the magnitude and direction of the electric force produced exerted by these charges on another charge q at the center of a face of the cube. Homework Equations 3. So far...

Homework Statement A metal sphere hangs from a string and has 6 kg of mass. The sphere has a charge of +3.7 µC. A uniform electric field is turned on and directed to the right. (a). What is the electric force on the metal sphere if the magnitude of the electric field is 106 N/C? (b)...

Homework Statement The sides of the triangular web have a length of a = 0.74 m, as depicted in the figure. Two of the spiders (S1 and S3) have +6.6 µC charge, while the other (S2) has −6.6 µC charge. a.) What are the magnitude and direction of the net force on the third spider (S3)? I...

Where is the potential zero? 1. Where is the potential zero between a negative (-.03c) and a positive charge (.27) separated by 1 meter? 2. Point charges laws 3. My textbook doesn't mention where is potential zero between two charges, it's easy to solve if i know the point is in between or...

Hello. I am not sure if I must post here. The problem is not for homework, it derived from a classmate's question. Homework Statement We have a large quantity of liquid dielectric with relative permittivity \varepsilon and a charge Q immersed in the liquid in depth h. We bring another...

Homework Statement Four charges are placed at the corners of a square of side length a, as follows : -Q on the top left corner, +Q on the top right corner, -Q on the bottom left corner and +Q on the bottom right corner. Determine the electric field at the centre of the square and determine...

Homework Statement A finite uniform linear charge ρ_L = 4 nC/m lies on the xy plane; start point and end point are (7,0,0) and (0,7,0) .While point charges of 8 nC each are located at (0, 1, 1) and (0, -1, 1). Find E at (0, 0 ,0) Homework Equations dE=ρ_L *dz'/4∏ε *...