Question

two charges each of +q units are placed along a line. A third charge 'Q' is placed between them. At what position and for what value of 'Q', will the system be in equilibrium?

Answer 1

 Two point electric charges of values q and 2q are kept at a distance d apart from each other 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 the position of charge Q in terms of q and d...??? 


plz explain me in brief...