When there is no electric field inside a solid conductor, which of the following statements is correct?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → The free electrons inside the conductor move randomly due to thermal motion.
Without an electric field the free electrons still move at high speeds because of their thermal energy, colliding with the ions and changing direction at random. Their velocities point equally in all directions, so the average velocity is zero and there is no net flow of charge.
Option (1) The free electrons inside the conductor move randomly due to thermal motion. — Correct. This is the random thermal motion described above.
Option (2) The free electrons stay at rest. — Incorrect. The free electrons are never at rest; they keep moving because of their thermal energy.
Option (3) The positive ions in the conductor move in a direction opposite to the electrons. — Incorrect. The positive ions are fixed in the lattice and only vibrate about their mean positions; they do not drift.
Option (4) The random motion of free electrons contributes to the drift of electrons — Incorrect. Random motion gives zero average velocity, so it produces no drift; a drift velocity appears only when an electric field is applied.
NCERT (2026-27):
Electric Currents in Conductors – “… Consider first the case when no electric field is present. The electrons will be moving due to thermal motion during which they collide with the fixed ions. An electron colliding with an ion emerges with the same speed as before the collision. However, the direction of its velocity after the collision is completely random. At a given time, there is no preferential direction for the velocities of the electrons. … So, there will be no net electric current.”