Match the LIST-I with LIST-II
| LIST-I | LIST-II | ||
| A. | Path executed by a charged particle in a uniform electric field when it moves at right angles to the direction of electric field | I. | circular |
| B. | Path followed by a charged particle under uniform magnetic field when it has two velocity components, parallel and perpendicular to the direction of magnetic field. | II. | straight |
| C. | Path followed by a charged particle in a uniform magnetic field, when it is injected normal to the direction of the magnetic field. | III. | parabolic |
| D. | Path followed by a charged particle when it moves in uniform magnetic field parallel to the direction of the magnetic field. | IV. | helical |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A-III, B-IV, C-I, D-II
The path depends on the direction of the force relative to the velocity.
(A) Path executed by a charged particle in a uniform electric field when it moves at right angles to the direction of electric field — this matches (III) parabolic. A constant acceleration \( qE/m \) acts across the initial velocity, as for a body projected horizontally under gravity.
(B) Path followed by a charged particle under uniform magnetic field when it has two velocity components, parallel and perpendicular to the direction of magnetic field. — this matches (IV) helical. The perpendicular component gives a circle; the parallel component carries the particle along the field.
(C) Path followed by a charged particle in a uniform magnetic field, when it is injected normal to the direction of the magnetic field. — this matches (I) circular. The force \( qvB \) is perpendicular to the velocity and acts as a centripetal force.
(D) Path followed by a charged particle when it moves in uniform magnetic field parallel to the direction of the magnetic field. — this matches (II) straight. \( \vec{v}\times\vec{B} = 0 \), so there is no force.
NCERT (2026-27):
Motion in a Magnetic Field – “… First consider the case of v perpendicular to B. The perpendicular force, q v × B, acts as a centripetal force and produces a circular motion perpendicular to the magnetic field.”
Motion in a Magnetic Field – “… The motion in a plane perpendicular to B is as before a circular one, thereby producing a helical motion (Fig. 4.6).”
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.”