Question

An ellipse has uniform linear positive charge density in upper half (total upper half part charge +Q) and uniform linear negative charge density in lower half (total lower half part charge -Q) as shown in figure. Here semi minor axis b < a semi major axis. Select the correct statement about the magnitude of electric dipole moment P of the ellipse

• A. $P=\frac{Qb}{2}$
• B. $0<P<\frac{Qb}{2}$
• C. $\frac{Qb}{2}<P<2Qb$
• D. $2Qb$

Answer 1

Answer: (B)

As electric dipole moment $p$ is a pair of equal and opposite charges $+Q$ and $-Q$ separated by some distance, hence

For ellipse,
semi-major axis $(b)<$ semi-minor axis $(a)$, as $b<a$
Hence, magnitude of dipole moment $p$ will be
$0<p<\frac{Qb}{2}$