Question

An electric dipole has the magnitude of its charge as $q$ and its dipole moment is $p$. It is placed in a uniform electric field $E$. If its dipole moment is along the direction of the field, the force on it and its potential energy are respectively

• A. $2q\cdot E$ and minimum
• B. $q \cdot E$ and $p\cdot E$
• C. zero and minimum
• D. $q\cdot E$ and maximum

Answer 1

Answer: (C)

zero and minimum

Answer 2

The total force on dipole is zero because F = q E is applied on each charge but in opposite direction. The potential energy is U = $- \overrightarrow{ p} \cdot \overrightarrow{E}$ which is minimum when $\overrightarrow{ p}$ and $\overrightarrow{E}$ are parallel.