A sample of HCl gas is placed in an electric field of $3 × 10^4 NC^{-1}$. The dipole moment of each HCl molecule is $6× 10^{-30} Cm$. The maximum torque that can act on this molecule is:

$1.8×10^{-26} N m$

The correct answer is Option (3) → $1.8×10^{-26} N m$

The torque $(τ)$ acting on a dipole in uniform electric field is -

$τ=pE\sin θ$

where,

Dipole moment, $p=6×10^{-30}$

Electric field, $E=3×10^4N/C$

The maximum torque occurs when $\sin θ=1$ is -

$τ_{max}=pE$

$=(6×10^{-30})(3×10^4)$

$=1.8×10^{-26} N m$