Electrostatic interaction rule: which statement correctly describes how like and unlike electric charges interact?

Introduction / Context:
Coulomb’s law governs the interaction between point charges and is a cornerstone of electromagnetism. Correctly recalling the qualitative rule helps in predicting forces, field lines, and potential energy changes in electric fields.

Given Data / Assumptions:

• Charges are stationary point charges in vacuum for the conceptual rule.
• We consider only sign-based interactions, not magnitudes.

Concept / Approach:
Coulomb’s law states F = k * |q1 * q2| / r^2, with direction determined by the signs: same signs produce repulsion, opposite signs produce attraction. Field-line models also visualize this: lines originate on positive charges and terminate on negative charges, drawing unlike charges together.

Step-by-Step Solution:
Identify sign combinations: (+,+) or (−,−) → repulsion.Opposite signs: (+,−) → attraction.Thus, the correct rule is “like repel, unlike attract.”

Verification / Alternative check:
Potential energy U = k * q1 * q2 / r shows positive U for like charges (repulsive) and negative U for unlike charges (attractive), consistent with the rule.

Why Other Options Are Wrong:
Any option claiming “unlike repel” or “like attract” contradicts Coulomb’s law and observed electrostatic behavior.

Common Pitfalls:
Mixing magnetic pole rules with electric charges; they are analogous but must be kept conceptually distinct.

Final Answer:
Like charges repel and unlike charges attract.