When dipole moment $\vec{P}$ is parallel to a non-uniform electric field $\vec{E}$,the net force on the electric dipole is . . . . . . .

Choose the incorrect statement from the following.

When an electric dipole $\overrightarrow{P}$ is placed in a uniform electric field $\overrightarrow{E}$,at what angle between $\overrightarrow{P}$ and $\overrightarrow{E}$ will the magnitude of the torque be maximum? (in degrees)

Electric field at the equator of a dipole is $E$. If both dipole moment and distance are doubled,then the electric field will be $:-$

If $E_{a}$ and $E_{q}$ represent the electric field intensity due to a short dipole at a point on its axial line and on the equatorial line at the same distance $r$ from the centre of the dipole,then

An electric dipole having each charge of magnitude $2 \mu C$ is placed in an electric field of intensity $8 \times 10^{4} \ N/C$. If the maximum torque acting on the dipole is $4 \times 10^{-3} \ N \cdot m$,the length of the dipole is: (in $mm$)