Match the LIST-I with LIST-II
| LIST-I | LIST-II | ||
|---|---|---|---|
| A. | An electric charge in uniform motion produces | I. | does not change its direction due to magnetic field |
| B. | A charge moving parallel to magnetic field | II. | a magnetic field only |
| C. | A static electric charge does | III. | experiences a force perpendicular to its motion |
| D. | An electric charge moving perpendicular to a uniform magnetic field | IV. | not produce any magnetic field |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → A-II, B-I, C-IV, D-III
Only a moving charge produces a magnetic field, and the Lorentz force \( q\vec{v}\times\vec{B} \) on it is perpendicular to \( \vec{v} \) and \( \vec{B} \).
(A) An electric charge in uniform motion produces — this matches (II) a magnetic field only, by elimination (see the note).
(B) A charge moving parallel to magnetic field — this matches (I) does not change its direction due to magnetic field. With \( \vec{v} \) parallel to \( \vec{B} \), the magnetic force is zero.
(C) A static electric charge does — this matches (IV) not produce any magnetic field. Only moving charges produce a magnetic field.
(D) An electric charge moving perpendicular to a uniform magnetic field — this matches (III) experiences a force perpendicular to its motion. The force is at right angles to \( \vec{v} \), so the charge moves in a circle.
Note: It seems that there is a mistake in the original NTA paper: a moving charge also produces an electric field. Option (4) is still the only option with B-I, C-IV and D-III.
NCERT (2026-27):
Sources and Fields – “… Just as static charges produce an electric field, the currents or moving charges produce (in addition) a magnetic field, denoted by B (r), again a vector field.”
Magnetic Field, Lorentz Force – “… The vector product makes the force due to magnetic field vanish (become zero) if velocity and magnetic field are parallel or anti-parallel. The force acts in a (sideways) direction perpendicular to both the velocity and the magnetic field.”