Three point charges -Q, Q and Q are placed on a straight line with distance d between charges as shown. Find the magnitude of the electric field at the point P in the configuration shown which is at a distance a from middle charge Q in the system provided that `a gt gt d`. Take `2Qd=p`.

Four point charges Q.q Q and q are placed at the corners of a square side 'a' as shown in the figures. Find the resultant electric force on a charge Q,

The point charges Q and -2Q are placed at some distance apart. If the electirc field at the location of Q is E , the electric field at the location of -2Q will be

Four point charges Q, q, Q and q are placed at the corners of a square of side 'a' as shown in the figure. Find the resultant electric force on a charge Q?

Two point charges +Q and -Q are separated by a certain distance. The resultant electric field is parallel to the line joining the charges at the points

Three charges -q,+Q and -q are placed in a straight line as shown If the total potential energy of the system is zero, then the ratio (q)/(Q) is

Four point charges +q,+q,-q and -q are placed on the corners of a square of side length 'a' as shown in the figure. The magnitude of electric field at a point which is at a distance x (gt gt a) from the centre along a line perpendicular to the plane of the square and passing through the centre is