Using the expression for the torque acting on an electric dipole placed in a uniform electric field, define electric dipole moment.

Explanation

Torque acting on an electric dipole placed in a uniform electric field is given by:
`vecpi= vecp xx vecE" "implies" "pi=pE sintheta`
If`" "E=1 and theta =90^(@)` then `p=pi`
Thus, dipole moment is numerically equal to the torque acting on the dipole, if it is placed at right angle to the uniform electric field of unit magnitude.