Question

The flow of the electric current through a metallic conductor is:
(A) Only due to electrons
(B) Only due to +ve charges
(C) Due to both nuclei and electrons,
(D) Cannot be predicted.

Answer 1

Hint : The nuclei of the atoms are bonded to each other due to interatomic forces. Some electrons are loosely bound to their atoms thus respond to electric fields.

Complete step by step answer
When a potential difference is applied across the ends of a metallic conductor, generally current, is said to flow within the conductor.
Now, usually the nucleus of the atoms are often very stable due to the intermolecular forces between them and other atoms or molecules, hence it bounds them to one another. Any force that tries to move one will tend to move the others. Hence, when the voltage is applied, the nuclei tend to remain in their position. Hence, current is certainly not due to the nuclei of the atoms.
On the other hand, in a metallic conductor, there exist certain electrons that are said to be free. These electrons are called free electrons.
Free electrons are electrons are the electrons which actually respond significantly to application of voltage. When a potential is applied across the ends of the conductor, which implies the presence of an electric field, these electrons, being charged and unbounded to each other or other atoms, respond to the applied field move in the opposite direction of the field. This is simply because the electrons are negative. This movement of electrons is what constitutes current.
Hence, the correct option is A.

Note
Although, we have categorised the electrons which allow conduction as free electrons, but in the actual sense, these electrons do have some atomic bond (attractive force between the nucleus proton and the orbital electrons) with the nucleus of the atom. They are usually the one to two electrons at the outermost shell of metals and are thus very loosely bound to the atoms due to the weakened electrostatic field of the nucleus protons at the far distance.