Chapter 18, Problem 1Q

When an electric cell is connected to a circuit, electrons flow away from the negative terminal in the circuit. But within the cell, electrons flow to the negative terminal. Explain.

To determine

To explain:

The reason for the electrons flow to the negative terminal inside the battery

Answer to Problem 1Q

Solution:

Correct and short answer to the query is, “to complete the loop of electrons and to maintain the negative terminal rich of electrons, it is necessary that inside the battery, the electrons should move to the negative terminal.”

Explanation of Solution

In the external circuit, electrons are pushed away from the negative terminal of the battery because the electrons too have negative charge and we know that similar charges repel each other. Therefore, in external circuit of a battery, electrons travel from the negative terminal to the positive terminal.

But inside the battery, the direction of flow of electrons is reverse, i.e. from positive terminal to the negative terminal. It happens because inside the battery a continuous chemical reaction takes place. The two electrodes of the battery are made of different materials and they have different chemical stabilities. Only one electrode can pull the electrons towards it and that’s why it is called negative electrode, as the accumulating electrons make the electrode negative. So when an external conducting wire is connected between the two electrodes, the electrode which is negative due to the accumulation of electrons of the battery pushes the external electrons away from it.

As in the outer circuit, the electrons keep on moving away from the negative terminal, the number of electrons at that electrode decreases but because of simultaneous chemical reaction inside the battery, sufficient number of electrons reach to the negative terminal of the battery from inside the battery. Hence inside the battery, the electrons keep on moving towards the negative terminal; otherwise it cannot be maintained ‘negative’ for so long.