To sketch equipotential lines for an isolated negatively charged particle, recognize that these lines are always perpendicular to electric field lines. Electric field lines originate from positive charges and terminate at negative charges, meaning they will extend radially inward toward the negatively charged particle from infinity. The equipotential lines will be circular and centered around the particle, indicating regions of equal electric potential. Understanding these relationships is crucial for accurately representing electric fields and potentials in diagrams. This knowledge is essential for studying electrostatics and related concepts.