Question: Q. 7. Two dipoles, made from charges $\pm q$ and $\pm \mathrm{Q}$ respectively, have equal dipole moments. Give the (i) ratio between the ‘separations’ of these two pairs of charges, (ii) angle between the dipole axes of these two dipoles.
U] [O.D. I, II, III 2013; CBSE SQP 2013]
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Solution:
Ans. As $q a=Q a^{\prime}$, we have
$$ \frac{a}{a^{\prime}}=\frac{Q}{q} $$
and
$\theta=0^{\circ}$.
[CBSE Marking Scheme, 2013]
Detailed Answer :
If distance between two charges of dipoles be $l_{1}$ and $l_{2}$ respectively, then dipole moments of dipoles will be $q l_{1}$ and $Q l_{2}$
(i) ratio between the separations of two pairs of charges $q, Q$
$$ \begin{aligned} & q l_{1}=Q l_{2} \ & \text { or, } \quad \frac{l_{1}}{l_{2}}=\frac{Q}{q} \end{aligned} $$
(ii) angle between dipole axes of two dipoles will be zero.
