Which of the following is true?

The correct answer is Option (1) → A circulating electron in an atom can be regarded as a current-carrying loop.

Option (1) A circulating electron in an atom can be regarded as a current-carrying loop. — Correct. An electron orbiting the nucleus is a charge going round a closed path. So it is equivalent to a current-carrying loop and has an orbital magnetic moment. In a bulk material these moments add up to give its magnetisation.

Option (2) Magnetic monopoles exist. — Incorrect. Isolated magnetic poles are not known to exist. A bar magnet broken into two halves gives two smaller magnets, each with a north and a south pole.

Option (3) A bar magnet is analogous to a charged rod. — Incorrect. A bar magnet, with its north and south poles, is analogous to an electric dipole. Its field at large distances follows from the dipole field with \( \vec{p} \) replaced by \( \vec{m} \).

NCERT (2026-27):
Diamagnetism – “… Electrons in an atom orbiting around nucleus possess orbital angular momentum. These orbiting electrons are equivalent to current-carrying loop and thus possess orbital magnetic moment.”