If a charge q is placed at the centre of the line joining two equal charges Q such that the system is in equilibrium then the value of q is

A charge q is placed at the centre of the line joining two equal charges Q. If the system of the three charges is in equilibrium, then what will be the value of q?

A charge q is placed at the centre of line joining two equal charges Q. Show that the system of three charges will be in equilibrium if q = -Q/4

A charge q is placed at the centre of the line joining two equal charges Q. The system of the three charges will be in equilibrium if q is equal to: