When an electron is introduced in a region of electric field, it starts accelerating in the direction opposite to the field. Choose the correct statement among the following.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → The electric field does positive work on the electron and its potential energy decreases.
The force on an electron is \( \vec{F} = -e\vec{E} \), opposite to the field. It starts from rest, so it moves along the force.
The field does positive work, because the displacement is in the direction of the force:
\( W = Fs\cos 0^{\circ} = Fs \gt 0 \)
The work done by a conservative force equals the decrease in potential energy:
\( \Delta U = -W \lt 0 \)
So the potential energy of the electron decreases, and its kinetic energy increases by the same amount.