The paths of electrons between successive collisions with the fixed positive ions of the metal, in the presence of electric field are :
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → curved
Between collisions an electron is acted on by a constant force \( -e\vec{E} \), so it has a constant acceleration opposite to the field. Its velocity just after a collision is in a random direction, so, like a projectile thrown at an angle under gravity, it moves along a curved path (an arc of a parabola) until the next collision.
Only in the absence of a field are the paths between collisions straight lines.
Why the other options are incorrect
Option (2) straight line in the direction of electric field. — Incorrect. The paths are not straight, and the force on an electron is opposite to the field, not along it.
Option (3) straight line in the opposite direction of electric field — Incorrect. The force is opposite to the field, but the electron’s velocity after a collision is in a random direction, so the path bends into a curve rather than running straight along the force.
Option (4) independent of presence of an electric field — Incorrect. Without a field the paths are straight lines; it is the field that curves them.
NCERT (2026-27):
Drift of Electrons and the Origin of Resistivity – “… (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? … (e) In the absence of electric field, the paths are straight lines; in the presence of electric field, the paths are, in general, curved.”