A circular loop is placed in the plane of the paper in a magnetic field \( \vec{B} \). A current is induced in the loop in an anticlockwise direction. This is because the magnetic field \( \vec{B} \) is
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → outward and decreasing with time
By Lenz's law the induced current flows so that its own magnetic field opposes the change in flux through the loop. By the right-hand rule, an anticlockwise current (as seen on the paper) produces a field outward (out of the paper) inside the loop. So the change it opposes is either a decrease of an outward field or an increase of an inward field.
Option (1) parallel to the plane of the loop and increasing with time — Incorrect. A field parallel to the plane of the loop sends no flux through it, so no current is induced at all.
Option (2) inward and decreasing with time — Incorrect. A decreasing inward flux is opposed by an inward induced field, which needs a clockwise current.
Option (3) outward and decreasing with time — Correct. The outward flux falls, and the induced current tries to keep it up by adding an outward field, which means an anticlockwise current.
Option (4) outward and increasing with time — Incorrect. A rising outward flux is opposed by an inward induced field, which needs a clockwise current.
NCERT (2026-27):
Lenz’s Law and Conservation of Energy – “In 1834, German physicist Heinrich Friedrich Lenz (1804-1865) deduced a rule, known as Lenz’s law which gives the polarity of the induced emf in a clear and concise fashion. The statement of the law is: The polarity of induced emf is such that it tends to produce a current which opposes the change in magnetic flux that produced it.”