Final answer:
Batteries maintain a constant potential difference by converting stored chemical energy into electrical energy. Charge density plays a role in creating voltage as it creates an electric potential difference.
Step-by-step explanation:
Batteries maintain a constant potential difference by converting stored chemical energy into electrical energy. This process involves the flow of electrons from the battery's negative terminal to its positive terminal, creating a potential difference or voltage.
Charge density, which refers to the amount of charge per unit volume, plays a role in creating voltage. When a battery is fully charged, the charge density is higher in the positive terminal compared to the negative terminal. This charge imbalance creates an electric potential difference, which drives the flow of electrons.