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Electrostatics is concerned with the electrical fields and scalar potentials of stationary electrical charges and charge distributions. Use this for questions about electromagnetic situations in which currents and magnetic fields are absent, otherwise use [tag:electromagnetism] and/or [tag:magnetic-fields]

How do you make out that there are 4 surfaces? Each surface is the boundary between air and metal. The conductor has only 2 boundaries. Excess charge exists only on the air side of each of these bound …
answered Mar 17 '17 by sammy gerbil
Both problems are quite difficult. The solution for the conducting disk is well-established and is given in Conducting Ellipsoid and Conducting Disk. The 1D needle could be modelled as an ellipsoid, …
answered Jan 3 '17 by sammy gerbil
The forces on the 2 charges are equal and opposite (Newton's 3rd Law). The electric field strength is $E=F/Q$. Therefore $\frac{E_1}{E_2}=\frac{Q_2}{Q_1}$.
answered Nov 9 '16 by sammy gerbil
The author is correct. The interaction energy $W_0$ is the electrostatic potential energy of the system of charges. This is the work required to assemble a charge distribution, or the negative of tha …
answered Aug 28 '18 by sammy gerbil
A neutral charge is not another kind of charge. It is no charge at all! Lines of force only start on +ve charges and end on -ve charges. They don't start or end on things which are not charges (ie n …
answered Nov 2 '16 by sammy gerbil
Electrostatic energy does not only depend on the charge on the object. It depends on the work done in bringing charge to it from infinity, where the potential energy is presumed to be zero. The polar …
answered Dec 9 '17 by sammy gerbil
No. The battery is already neutral, and remains neutral during operation. (-ve charge leaving one terminal has to be replaced at the other terminal.) If some -ve charge flowed to Earth the battery wo …
answered Jul 9 '16 by sammy gerbil
The voltage across the capacitor is not initially equal to the voltage of the battery. It is initially zero, as it was before it was connected to the battery. It does not change until the charge on it …
answered Nov 27 '16 by sammy gerbil
Yes, half the charge on the part of the shell which was removed is redistributed to the inner surface of the shell and half is redistributed on the outer surface. The electric field at the outer su …
answered Jul 9 '18 by sammy gerbil
You are correct. Rolling-up increases the capacitance of a parallel plate capacitor by a factor of up to 2 in the limit of many complete turns with a radius much larger than the separation of the plat …
answered Mar 8 '17 by sammy gerbil
The direction of the force is given by the tangent to the line of force (ie electric field vector) at the point where the particle is currently situated. If the particle were already moving and this …
answered Sep 2 '16 by sammy gerbil
Perhaps the phrase should be quasi-static equilibrium. This means that the particle moves so slowly that it does not gain any kinetic energy. At each point on its path the electrostatic force on the p …
answered Nov 21 '17 by sammy gerbil
The relation $\delta l = r_{eff}\delta \theta$ is not correct because it does not take into account the orientation of the line element $\delta l$ relative to the line element $r_{eff}$. For example, …
answered Sep 25 '17 by sammy gerbil
Yes your assumptions are correct but they do not quite agree with what you have drawn. The charge on the surface of the metal sphere is $-2q$. But if the 3rd charge is much further away than the radi …
answered Mar 4 '17 by sammy gerbil
Point charges are mathematical abstractions. Real charges have a finite radius. Even for an object as small as an electron, there is some distance from the centre at which the inverse square law brea …
answered Mar 29 '17 by sammy gerbil

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