Potential Loss, internal resistance

Question

When electron flows from positive terminal to negative terminal inside battery, it gains energy but at the same time loses voltage( potential drop) Why two contradictory incidents are occurring ?

Answer 1

When electron flows from positive terminal to negative terminal inside battery, it gains energy...

Yes. Chemical potential energy in the battery is converted to electrical potential energy of the electrons.

...but at the same time loses voltage( potential drop) Why two contradictory incidents are occurring ?

There is no contradiction. The electrical potential energy acquired by the electrons in the battery is converted to or stored in other forms in the circuit connected to the battery. Energy is conserved.

Hope this helps.

Answer 2

I see no contradiction; the energy is converted from one form to another. When electrons accelerate in a field, they gain kinetic energy in exchange for potential energy. Energy is conserved.

Answer 3

I wonder if what you're missing is that potential difference (voltage) is defined in terms of a positive test charge: The increase in potential in going from A to B is the work needed (because of the presence of an electric field) per unit test charge to move a positive test charge from A to B.

And, as you well know, an electron has a negative charge, so it gains electrical potential energy as it goes from the + to the – terminal, though the – terminal is at a lower potential, because a positive test charge would lose electrical potential energy in going from the + terminal to the –.

The drop in potential is dependent on the more or less arbitrary convention of a positive test charge, whereas the electron's gain in electrical potential energy can is not a matter of convention: the chemical mechanism of the battery has to do work pushing the electron from the + plate to the — plate against the force due to the electric field. There is therefore no contradiction in the Physics.