The phrase "closed lines of force" refers to a concept in physics, specifically in electromagnetism, describing magnetic field lines that form closed loops.

बंद बल रेखाएँ

English Usage: The magnetic field is illustrated by closed lines of force emanating from the magnet.

Hindi Usage: चुंबकीय क्षेत्र को चुंबक से निकलने वाली बंद बल रेखाओं से दर्शाया गया है।