In the (i) absence of electric field, and in the (ii) presence of electric field, the paths of electrons between successive collisions with the positive ions of the metal, are
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (i) Straight line, (ii) Curved in general
Between two collisions an electron moves under the force on it.
(i) With no field there is no force, so the electron moves with constant velocity in a straight line until the next collision.
(ii) With a field \( \vec{E} \) the electron feels a force \( -e\vec{E} \) and has an acceleration \( \vec{a} = -e\vec{E}/m \). Its velocity changes continuously, so the path between collisions is curved in general (a parabola, like a projectile in a gravitational field). It is straight only if the electron happens to start along the direction of the field.
NCERT (2026-27):
Drift of Electrons and the Origin of Resistivity – “… Example 3.2 … (e) Are the paths of electrons straight lines between successive collisions (with the positive ions of the metal) in the (i) absence of electric field, (ii) presence of electric field?”
Drift of Electrons and the Origin of Resistivity – “… (e) In the absence of electric field, the paths are straight lines; in the presence of electric field, the paths are, in general, curved.”