1. A

    A mathematical doubt in the expression for the energy of a continuous Charge Distribution.

    I'm studying Introduction to Electrodynamics by David J.Griffiths and here I'm gonna present his method of calculating the the energy stored (or work done in assembling) of continuous charge distribution. W = \frac{1}{2} \int \rho V~d\tau d\tau stands for volume element. By Gauss' Law...
  2. C

    Help electrostatics - electric field(beginner level)

    The figure below shows three electric charges q1, q2 and q3 that are located at distances of r1= 2 cm, r2= 2cm and r3= 1cm from the origin of the coordinate system, as shown in the figure. Knowing that θ1 = θ2 = θ3 = 30º, q1=1mC,q2=3mC and q3=-2mC. Consider: 1/4πξº = 9x10 ^ 9 Nm² / C², and...
  3. C

    Electrostatics problem

    from the attachment, I have shown the following proof. However, there's another part to this question which I'm having a little trouble with. The question is as follows: Hence, show that ∇xE and ∇·E are both equal to zero at position P(x,y,z), unless x = y = z = 0. What happens at the...
  4. P

    Electrostatics impossible question. Please help!

    Well, i recently gave my O-Level Physics (5054) exam, and i found one of the MCQ's about electrostatics pretty tricky, and it got me thinking. I would like to share it, and i really want to see what others think about this. I asked my teacher, but he can't come up with an explanation! So...
  5. J


    Question : A charge, q, is placed at the center of a closed cube, of side a. What is the electric flux through each face of the cube? My answer : General formula for Electric Flux : E*S [Where E is the electric field and S is the area] Distance of charge q from any one face : a/2...
  6. S

    Electrostatics question, find distance

    6.2) F = k*q1*q2/r^2 6.17 = (9*10^9)(5.5*10^-6)^2/r^2 r = 0.21m and not 0.32m I think that 0.32m is wrong, or am I doing something wrong? Forgot to add one more question: 6.3) Point S is 0,15 m to the right of the centre of sphere A. Calculate the magnitude and...
  7. S

    Doubts in electrostatics

    I have a few questions pertaining to some concepts in electrostatics, I'd be grateful if someone would help me out. 1) When we place a positive point charge inside a hollow conducting sphere, at its center, field lines emerge uniformly from the sphere. Okay, easy enough. Now, if we place...
  8. S

    Electric field at center of a disk

    We've just begun electrostatics in school. I can't seem to understand why the field at the center of a uniform charged disk is not equal to zero. We found the formula for its field by assuming the disk to be made up of charged rings and then integrating it. The field at the center of a ring is...
  9. D


    Protons are being accelerated through a potential differenceof 5.00x103 V in the gun of a particle accelerator. Theymust pass between two parallel deflecting plates that are6.0x102 m long and 2.0x10-2 m apart with apotential difference between them of 1.50x103 V. a) What is the kinetic...
  10. S

    electrostatic experiments not work well on humid day

    Why do electrostatic experiments not work well on humid day? Should the reason be the moisture coats the surface of the material, providing a low-resistance path for electron flow or the water molecules in the atmosphere deplete some of the delocalized charges? Which one is more significant...
  11. A

    electrostatics question

    1. Consider a circular ring of radius 'a' which carries a uniform line charge density ρL as shown in the figure below. Calculate the electric field at a point P (0, 0, h) on the z axis (z > 0). i was given a diagram with this question aswell but i cant paste it. i dont...
  12. A

    Electrostatics Equilibrium Question

    A charge of 2.9 nC and a charge of 5.8 nC are separated by 40.80 cm. Find the equilibrium position for a -5.0 nC charge.
  13. S


    Two point charges q and 2q are placed distance d apart in air. A third charge Q is to be kept along the same line in such a way that the net force acting on q and 2q is zero. Calculate position of Q in terms of q and d. My working -: F01 due to q(free space/vacuum) = \frac {1} {4\pi...
  14. J

    Applications of electrostatics

    I want to know that applications have electrostatics in the engineering of telecomiunicaciones. Thanks
  15. A

    electrostatics question

    Hey guys. I have a question about this question... Can I see this slab as a disk with radius a? And if so, does the electric field work only on z axis? (above and beneath the disk) Thanks a lot.
  16. A

    one-dimensional lattice (electrostatics)

    Hey guys. So, I got this question in the pic. First of all, I drew what I think to be a one-dimensional lattice (in the green box) but I'm not sure, is it right? Second of all, I don't really understand the question, I mean I know that a potential energy of charge q is V(r) = kq/r when you say...
  17. A

    electrostatics question

    Hey guys. Is it correct what I did there? Thanks in advance.
  18. I

    Hard electrostatics question

    1. The problem statement, all variables and given/known data An object with a charge of +4.0 x 10^-18 C and a mass of 1.1 x 10^-15 kg is held stationary by balanced gravitational and electric forces midway between horizontal charged plates as shown. What is the applied voltage V? 2. Relevant...
  19. I

    electrostatics question

    1. The problem statement, all variables and given/known data A 2.5C charge is moved from a point with a potential of 12V to another point of potential 75V. How much work was done on this charge? 2. Relevant equations ΔV = ΔEp/Q 3. The attempt at a solution I am unsure how to do this question...
  20. I


    Question: A proton, accelerated from rest through a potential difference of 1.2 x 10^4 V, is directed at a fixed 5.0 x 10^-6 charge. a) What is the speed of the proton as it leaves the parallel plates? b) What is the distance d from the fixed charge when the proton is stopped? Attempt...