Two charges A and B are fixed in place, at different distances from a certain spot. At this spot the potentials due to the two charges are equal. Charge A is 0.22 m from the spot, while charge B is 0.47 m from it. Find the ratio qB/9A of the charges.

A capacitor is composed of two metal plates. The two plates have the dimensions L = 0.11 m and W = 0.56 m. The plates have a distance between them of d = 0.1 m, and are parallel to each other.  Part (a)  The plates are connected to a battery and charged such that the first plate has a charge of q. Write an expression for the magnitude of the electric field, |E|, halfway between the plates.  Part (b)  Input an expression for the magnitude of the electric field, |E2|, just in front of plate two.  Part (c)  If plate two has a total charge of q = -1 mC, what is its charge density, σ, in C/m2?

An electrostatic paint sprayer has a 0.25 m diameter metal sphere at a potential of 25.0 kV with respect to the ground that repels paint droplets onto a grounded object.    Part (a)  What charge is on the sphere, in coulombs?  Q =   Part (b)  What charge, in coulombs, must a 0.12 mg drop of paint have in order to arrive at the object with a speed of 10.0 m/s, starting from rest?  q =

Four equal negative charges, of magnitude 10C are situated at the corners of a square, with a length of side equal to 3. A small test charge of 0.07C is placed in the exact centre of the square. What is the magnitude of the potential energy of the test charge? Give your answer in GJ