JEE Main 2023 · 10 April · evening · Single correct · +4 / −1
In a metallic conductor, under the effect of applied electric field, the free electrons of the conductor
- (a) move in the straight line paths in the same direction
- (b) move with the uniform velocity throughout from lower potential to higher potential
- (c) drift from higher potential to lower potential.
- (d) move in the curved paths from lower potential to higher potential
Answer and solution
Answer (d) move in the curved paths from lower potential to higher potential
Solution
Physics sir · 4 steps
Electrons carry negative charge, so they drift against the field, from low to high potential, in bent paths.
- Random motion first. With no field, free electrons move randomly at high speed and keep colliding with the ions of the lattice. Their average velocity is zero.
- Direction of drift. The force on an electron is F⃗ = -eE⃗, opposite to the field. The field points from higher to lower potential, so electrons are pushed from lower potential to higher potential.
- Shape of the path. Between two collisions this constant force bends each electron's path, much like a projectile under gravity. So every free path is curved, and the electron keeps speeding up and losing speed in collisions. It never moves with uniform velocity.
- So. The electrons move in curved paths, with a slow net drift from lower to higher potential. That is option (d).
The idea to keep. Electrons drift opposite to the electric field, so from low to high potential. Collisions and the steady force bend their paths, so think curved zig-zags with a small net drift, never straight lines.
Answer from the NTA final answer key. Solution by PrepWiser.