Four charges are kept at the corners of a square of size a. Three charges are -Q and one is 3Q. Calculate the net electric dipole moment of this system.

Explanation

We can visualise the system as three different electric dipoles as shown in the figure.
Charge 3Q can be considered as three equal charges . Each part is considered along with one of the other negative charges to make three dipoles . Two dipoles are having dipole moment `p_1=Qa`. The one along diagonal of square `p_2=Qasqrt2`.
Net dipole moment will be along `p_2` and its magnitude can be calculated as follows :
`p=p_1sqrt2+p_2`
`p=2sqrt2Qa`