Two beakers with different levels of water are connected using a pipe. The potential difference makes the water flow until the levels become the same. A water pump is required to maintain the potential difference for a continuous water flow. Similarly, if an electric field is applied to an isolated conductor, current starts to flow. Hence, a net positive and negative charge accumulates at opposite ends. They produce an equal and opposite electric field, making the total electric field zero, thus stopping the current. To maintain a steady current in a circuit, it should be supplied with a device called a battery, which acts like a pump. Inside a battery, because of the electrostatic field, an electron experiences a force. The battery's chemical energy provides a non-electrostatic force, which pushes it from the positive to negative terminal against the electrostatic force. This force maintains the potential difference between the terminals, converting chemical energy into electrical energy. After reaching the negative terminal, the electrons move toward the positive terminal to complete the circuit.