Point charge Definition and 345 Threads

Consider a capacitor which is just like a plate capacitor, but instead of the upper electrode being a plate it is a point charge Q. the lower plate is held at a fixed potential V=0. how could you calculate the capacitance of the system? when trying to calculate - it looks like it will be 0...

Hi, I read in the Feynman Lectures Vol II that the assumption that the electron is a point leads to an infinite energy in its field, and that the difficulty hasn't been resolved. Has there been any progress on this since Feynman gave his lectures?

Hi everyone, I have some queries regarding the situation where a point charge is placed at a distance from an infinite conducting plane:say the plane is the xy plane and the charge is above it at distance z: 1) If the plane is at non-zero potential, is that true that the plane will not...

Homework Statement A point charge q is located in the xy plane near two grounded conducting planes intersecting at right angles as shown in the Figure. The z axis lies along the line of intersection of the planes. Find and justify (mathematically show) the force acting on this charge q...

Homework Statement The value of the Electric field at a distance of 82.8 m from a point charge is 75.3 N/C. Its direction is radially in toward the charge. The Coulomb constant is 8.98755 E9. Find the magnitude and sign of the point charge at the origin. Answer in units C. Homework...

Hi, So, assuming the theoretical existence of a monopole, we would have to alter the maxwell equations to give the magnetic field a divergence, and also to ensure that the divergence of the curl of the electric field is still zero we would have to add a term. The altered divergence of B would...

Hi all this is my first post. This looks like a great forum and hopefully I can contribute in some way to the discussion. I have a question about JPEG I attached; hopefully you all can see it. What is the strategy for "reducing the charges"? For instance, why is -3q reduced to -2q and...

I just have a general question. Coulomb's Law is ... F=\frac{k\cdot |q_1||q_2|}{r^2} Ok, solving this question ... Three point charges are arranged along the x-axis. Charge q_1=+3.00\mu C is at the origin, and charge q_2=-5.00\mu C is at 0.200 m. Charge q_3=-8.00\mu C. Where is q_3...

Homework Statement A particle with mass m and chare, q<0, moves in the field of a POINT charge Q>0, which is fixed in the origine of a cartesian coordinate system. The particle starts at REST in a distance R on the x-axis of a cartesian coordinate system : r(o)(vector) = Rix(vector), V(o)...

OK I'm really not understanding any of this, please help, and any tips on how to go about problems like this in general would be much appreciated. Homework Statement A point charge Q is situated a distance d from an infinite conducting plate connected to ground. Show that the total charge...

I have the problem A positive point charge of magnitude 2.4 micro Coulombs is at the center of an uncharged spherical conducting shell of inner radius 65 cm and outer radius 85 cm. I have been trying to calculate the total charge for the inner sphere. I solved for the Electric Field by...

Two point charges are placed on the x axis. The first charge, q1 = 8.00nC , is placed a distance 16.0 m from the origin along the positive x axis; the second charge, q2 = 6.0nC , is placed a distance 9.00m from the origin along the negative x axis. Find the electric field at the origin...

b]1. Homework Statement [/b] Point charge q1= -5.00 is at the origin and point charge q2= +3.00 is on the -x axis at x= 3.00 cm. Point P is on the y-axis at y= 4.00 cm . Calculate the electric fields E1 and E2 at point P due to the charges q1 and q2. Express your results in terms of...

Homework Statement Two Positive charges q1 = q2= 2.0 microC are located at x=0, y = .30 m and x =0, y =-.30m. Third point charge Q =4.0 microC is located at x=.40 m, y = 0. What is the net force magnitude and the direction on charge q1 exerted by the other two charges. Homework Equations...

Homework Statement A point Charge Q is placed a distance R from the center of a conducting sphere of radius a, with R>a, i.e. the point charge is outside the sphere. The sphere is grounded- connected to a distant, unlimited source/sink of charge at zero potential. (Neither the distant...

hi everyone, if a stationary point charge is placed in an increasing magnetic field, is the force on the charge due to the magnetic field = 0? because Fb = qv*B and v=0 then how would I derive the magnitude of the force on the charge due to the magnetic field with the magnetic field...

Homework Statement three point charges, each of 10^-9 are located at 3 corners of a square of side 20cm. Calculate the electric potential at the forth corner. Homework Equations V = Q / (4(pi)(epsilon 0) r) The Attempt at a Solution Potential because of corner A = 10^-9 / (4...

Homework Statement A point charge of 43 microcoulombs is located a distance 48 meters from an infinite plane. Determine the electric flux through the plane due to the point charge. Homework Equations flux = integral E d A = enclosed charge / epsilon_0 E = kQ / r^2 The Attempt at a...

A thin rod 39.2 cm long is charged uniformly with a positive charge density of 72.0 mC/m. The rod is placed along the y-axis and is centered at the origin. A charge of +46.5 mC is placed 68.4 cm from the midpoint of the rod on the positive x-axis. Calculate the electric field at a point on the...

Why does an enclosed point charge have zero divergence/flux? Mathematically I can see that when the divergence operator is applied to E=q/r^2 (pointing in the r direction) I get zero, but what is the physical explanation for what is going on? I am confused because other enclosed electric fields...

Homework Statement The electric potential at a distance of 20.5 cm from a very small charged sphere is 33.0 V, with the potential taken to be zero at an infinite distance from the sphere. If the sphere is treated as a point charge, what is its charge? Homework Equations V = \frac {U}...

Hallo! Homework Statement Consider electrostatic Potential of point charge at point (0,0,0) \phi = 1/r I'm trying to calculate \Delta\phi Homework Equations The Attempt at a Solution Actually it's not a difficult problem outside (0,0,0): \nabla\phi = -\frac{\vec r}{r^3} \Delta\phi = 0 But...

Homework Statement A point charge of -8 µC is at the origin. What is the electric potential at (a) (3.0m, 0), (b) (-3.0m, 0), and (c) (3.0m, -3.0m)? Homework Equations V=kq/r The Attempt at a Solution a & b) V=(8.99x10^9)(-8x10^-6)/3 V= -23973.3 c)...

Griffiths problem 8.4 1. Homework Statement Consider 2 eual point charges q, separated by a distance 2a. Construct the plance equidistnace form the two charges. By integrating Maxwell's stress tensor over the plane determine the force of one charge on the other. Homework Equations...

My problem is this, Find the electrix flux through the top side of a cube. The cube's corner is on the origin, and is 'a' units on length. The charge 'q' is located at the origin, with the corner of the cube. I am thinking I need a double integral. One to swipe the box in the y direction...

Two infinite conducting plates 1 and 2 are separated by a distance l. A point charge q is located between the plates at a distance x from plate 1. Find the charges induced on each plate. I solved this problem assuming (intuitively) that a potential difference between plate 1 and 2 equals 0 and...

If the electron is a point charge, then its' charge to mass ratio approaches infinity. How does the Standard Model (QED) deal with this?

Hello all.. Here's a question I need some help with... A point charge +Q has been placed between two infinitely large conducting plates. The charge induced on the surface of the first plate is q_{1}. What should be the charge induced on the surface of the second? (Diagram attached; the...

A positive point charge q is placed at x=a and a negative point charge -q is placed at x=-a. a: find the magnitude of the electric field and the direction at x= 0. b: derive an expression for the electric field at points on the x-axis. use results to graph the x-component of the electric field...

A charge is spread uniformly along the y-axis from y=0 to y=∞. The charge density on the y-axis is λ. Find the force on a point charge q placed on the x-axis at x=x0

Please Help! I would really appreciate some help on this one...I'm pretty sure I'm making it harder than it is... The question is this - "Three point charges are fixed to the corners of a square, one to a corner, in such a way that the net electric field at the empty corner is zero. Do...

I need help with this question. I can't see the motion. I have Consider a solid sphere of radius R with a charge Q distributed uniformly. Suppose that a point charge 'q' of mass 'm', with a sign opposite that of Q, is free to move within the solid sphere. Charge q is placed at rest on the...

Hvae a look at the diagram Caluclate the force on the point charge q, due to a uniformly charged rod of length L a distance x from the point charge q. Discuss the limit when L approaches infinity with lambda = Q/L fixed. Q = \lambda L dQ = \lambda dL Force of dQ on the point charge q...

Hi, I need help on the following question: Suppose a point charge q is constrained to move along the x-axis. Show that the fields at points on the axis to the RIGHT of the charge are given by \vec{E} = \frac{q}{4\pi\epsilon_0}\frac{1}{r^2}(\frac{c+v}{c-v})\hat{x} and \vec{B} = 0 What...

1. parallel plate with capacitor of 20uF, plate is 0.5mm apart. Find 1. Area of each plate 2. potential difference if there's a change of magnitude of 30uC on each plate. 3. stored energy 4. electric field between the two plates 5. charge density on the plate. |_| |_|...

Point Charge Check!? Hi, I' did this problem but for some reason I'm not getting the right answer. If you could check to see where I made my mistake I'd really appreciate it. Thanks! The problem: A poitn charge (m=1 g) at the end of an insulating string of length 55 cm is observed to be...

Hello guys, I have a question which I think I solved it right but I don't understand why the final answer is wrong. Here's the problem: Consider three charges as shown. k is 8.98755 * 10^9 N m^2/c^2. What is the electric field at a point 1.01 cm to the left of the middle charge? Ans. in N/C...

We haven't really covered this in class so I need some help. Assuming that these contours are those of a point charge at the origin, calculate the value of the charge in C. I tried using the equation kQ/R but that's wrong, I'm not even sure I'm using it right in fact. Any help? Thanks

This is SUPPOSED to be easy but i seemingly find find it hard... A poin charge of +Q is places a distance d/2 above the centre of a square surface of side d. Find the electric flux through the square. so i know that E dA = EA (because the flux through the square is all at 90 degree...

Question: Three point charges, which are initially at infinity, are placed at the corners of an equilateral triangle with sides d. Two of the point charges have a charge of q. If zero net work is required to place the three charges at the corners of the triangle, what must the value be of the...

I've been asked to complete electric field E and potential V inside and outside of a simple plate capacitor (the plates are infinitely large and the distance between the two plates is d.) My working is as follows. Inside the cap- E = \frac{ \sigma } { \epsilon_{o} } then potential V=Ed...

an electron with a speed of 5.00 x 10^8 cm/s enters an electric field of magnitude 1.00 x 10^3 N/C, traveling along field lines in the direction that retards its motion. a) How far will the electron travel in the field before stopping momentarily b) how much time will have elapsed c) in the...

if u have an uncharged,perfectly conducting hollow sphere of thickness t and radius R, and a point charge Q is placed a distance D from the centre of the sphere so that R-t>D, what would the electric field, E, be? i just treated it the same as if Q was in the centre of the sphere and the...

Inside an uncharged, perfect conducting hollow sphere of thickness t and radius R, a point charge Q is placed at a distance D from the centre, where D<R - t. Need to derive a simple expression for the field outside the sphere. In a section passing through Q, sketch qualitatively the charge...

"A proton with a speed 10^7 m/s enters a region of a uniform magnetic field B = .8 T, which is into the page. The angle is 60º Find the angle 'fi' and distance d" "which is into the page." What the heck does that mean!?