KEAM 2019 Physics and Chemistry Paper

The given electric field is uniform in nature. Thus, the net force acting on it will be zero. However, couple of forces will act on either charges of the dipole in opposite direction that would constitute torque. Due to this torque the dipole would rotate.
As, torque on the dipole is given as τ=p×E
Given, p0=P0⋅

⋀

k

and E=E0(2

⋀

i

−3

⋀

j

+4

⋀

k

), then
τ=(P0⋅

⋀

k

)×E0(2

⋀

i

−3

⋀

j

+4

⋀

k

)
=E0[2P0

⋀

j

−3P0(−

⋀

i

)]
[∵

⋀

k

×

⋀

j

=

⋀

j

and

⋀

k

×

⋀

j

=−

⋀

i

]=P0E0(3

⋀

i

+2

⋀

j

)
So, it implies that torque is acting on the dipole rotating it on x -y plane. However, the interaction energy between the dipole and electric field