91Ó°ÊÓ

• a)Charges of values, +2e and-2e.
• b) Separation between the charges, r =0.78 nm.
• c) Magnitude of the electric field,$E=3.4×{10}^{6}N/C$

Using the concept of the torque acting on a dipole, the torque for the given cases is given by considering the given situations of the angle made by the dipole to the electric field.

Formula:

The magnitude of torque $\left(\mathrm{Î\P }\right)$in terms of the magnitudes of the electric field E and the dipole moment p = qd is given by:

$\mathrm{Î\P }=pE\sin \mathrm{θ}$

From equation (i), we can see that the torque for$\mathrm{θ}=0°$ is given as:

$$\begin{gathered} \mathrm{Î\P }=pE\sin 0° \\ =0. \end{gathered}$$

Hence, the value of the torque is 0.

From equation (i), we can see that the torque for$\mathrm{θ}=90°$is given as:

$$\begin{gathered} \mathrm{Î\P }=pE \\ =\left(2.16×{10}^{-19}C\right)\left(0.78×{10}^{-9}m\right)\left(3.4×{10}^{6}N/C\right) \\ =8.5×{10}^{-22}N.m \end{gathered}$$

Hence, the value of the torque is$8.5×{10}^{-22}N.m$.

From equation (i), we can see that the torque for$\mathrm{θ}=180°$ is given as:

$$\begin{gathered} \mathrm{Î\P }=pE\sin 180° \\ =0. \end{gathered}$$

Hence, the value of the torque is 0.