Physics
Physics
Problem
An electric dipole has the magnitude of its charge as and its dipole moment is . It is placed in a uniform electric field . If its dipole moment is along the direction of the field, the force on it and its potential energy are respectively: (2004) a. and b. Zero and minimum c. and maximum d. and minimumIntuitive explanation
The key insight is that a dipole in a uniform field experiences a torque, not a net force—unless the field is non-uniform. Since this field is uniform and the dipole moment is aligned with it, the opposing charges feel equal and opposite forces that cancel out. For potential energy, think of it as the work needed to rotate the dipole from some reference; alignment with the field represents the lowest energy state, analogous to how a compass needle points north.
Intuitive explanation
The key insight is that a dipole in a uniform field experiences a torque, not a net force—unless the field is non-uniform. Since this field is uniform and the dipole moment is aligned with it, the opposing charges feel equal and opposite forces that cancel out. For potential energy, think of it as the work needed to rotate the dipole from some reference; alignment with the field represents the lowest energy state, analogous to how a compass needle points north.