Which charge carriers mainly carry the current in the following at room temperature?
A metal (conductor)
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Electrons
In a metal, the conduction band is partly filled or overlaps the valence band. So a large number of free electrons is available for conduction. There is no band gap to cross.
Option (1) Electrons — Correct. These free electrons drift under an applied electric field and carry the current. With \( E_g\approx0 \), they need no extra energy to take part in conduction. That is why a metal has a very low resistivity.
Option (2) Holes — Incorrect. Holes are the vacancies left in the covalent bonds of a semiconductor when electrons break free. In a metal, the free electrons carry the current.
Option (3) Protons — Incorrect. Protons are held in the nuclei of the metal ions, which stay fixed in the lattice, so they do not move through the metal.
Option (4) Neutrons — Incorrect. Neutrons are uncharged and bound in the nuclei, so they cannot carry a current.
NCERT (2026-27):
Classification of Metals, Conductors and Semiconductors – “… When there is overlap electrons from valence band can easily move into the conduction band. This situation makes a large number of electrons available for electrical conduction.”