Question

When the ends of metal wire are not connected to a battery:
A) Electrons move from positive electrode to negative electrode.
B) Electrons move from negative electrode to positive electrode.
C) Electrons move in random directions.
D) Protons move in a random direction in such a way that their net movement in a unit volume is zero.

Answer 1

Hint: Think whether current will flow in an isolated wire. And what changes occurs when the ends of metal wire is connected to the battery. Also keep in mind that whether electrons or protons are mobile or not.

Complete step by step solution:
This is a question of simple theory. When the wire is connected to a battery the electrons move in a specific direction due to the difference in the potential between the two terminals. They move from the negative terminal to the positive terminal. However there is no such potential difference developed when the metal wire is disconnected from the battery. Thus the electrons do not move in a specific direction. Being a metal wire and having free electrons, the electrons move in random directions in such a manner that their net movement is zero.

However protons are well bonded to the nucleus by strong nuclear forces. Hence they are immobile and do not contribute to flow of current. Thus only the free electrons can move.

Additional Information: Free electrons are those electrons which are loosely bonded to the nucleus. Hence they consist generally of the valence electrons. Being loosely bonded, they can easily move from one point to the other. Their movement is random. Presence of free electrons is a criterion for electrical conductivity.

Note: The movements of electrons are responsible for flowing current. The electrons only move in a specific direction when a potential difference is applied to it. There is no role of protons in current flowing. When the wire is connected across the two terminals of the battery the electrons flow from positive to negative through the wire which is outside the battery and move from negative to positive in the inside portion of the battery.