91Ó°ÊÓ

1. Electric field of magnitude,$E=40\text{N/C}$
2. Vertical axis scale,${\mathrm{τ}}_s=1.00×{10}^{−28}\text{Nm}$

Using the equation of the torque in the electric dipole, we can get the required magnitude of the torque with the given data.

Formula:

The torque acting on a dipole tends to rotate the dipole: (hence the dipole) into the direction of field,E is given by: $\mathrm{τ}=−pEsin\mathrm{θ}$ (i)

where,$\mathrm{θ}$ is the angle between p and E.

From equation (i), considering$\mathrm{θ}$as a variable, we note that it reaches its maximum value when,:

$\mathrm{θ}=−{90}^o$

${\mathrm{Ï„}}_{max}=pE$

Thus, with$E=40\text{N/C}$and(${\mathrm{τ}}_{\max }=1.00×{10}^{−28}\text{Nm}$determined from the graph), the dipole moment is given using above equation as:

$\begin{array}{c}1.00×{10}^{−28}\text{Nm}=p\left(40\text{N/C}\right)\\ p=2.5×{10}^{−30}\text{C.m}\end{array}$

Hence, the value of the dipole moment is.$2.5×{10}^{−30}\text{C.m}$