Consider an arbitrary electrostatic field configuration. A small test charge is placed at a null point (i.e., E = 0) of the configuration. Show that the equilibrium of the test charge is necessarily unstable.Verify this result for the simple configuration of two charges of the same magnitude and sign placed a certain distance apart.

Two point charges +q and -q are placed at distanced d apart. What are the points at which the resultant field is parallel to the line joininin the two charges?

+4e and +e are two charges separated by a distance 'a' m.Where should be a third charge 'q' be placed so that it is in equilibrium?

Two fixed point charges +9e and +4e are separated by a distance x.Where should a point charge be placed between the two charges, so that it is in equilibrium?

Two point charges Q and -3Q are placed at some distance apart. If the electric field at the location of Q is E, then field at the location of -3Q is

A shortbar magnet placedin ahorizontal plane has Its axis aligned along the magnetic north-south .direction. Null points are found on the axis of themagnet at 14 cm from the centre of the magnet. The earth’s magnetic field at the place is 0.36 G and the angle of.dip is zero. What Is the total magnetic field on the normal bisector of the magnet at the same distance as the null”point (i.e, 14 cm) from the centre of the magnet? (At null points, field due to a magnet Is equal and opposite to the horizontal component of earth’s magnetic field)