Final answer:
Voltage sources such as batteries and generators create a potential difference, resulting in an electric field that drives current as per Ohm's Law.
Step-by-step explanation:
Devices such as batteries, generators, and wall outlets are necessary for maintaining a current in an electrical circuit. These devices are sources of electromotive force, commonly referred to as voltage sources. A voltage source is a two-terminal device which can maintain a fixed voltage.
An ideal voltage source can maintain the fixed voltage independent of the load resistance or the output current. However, a real-world voltage source cannot supply unlimited current. A voltage source is the dual of a current source.They apply a potential difference (often symbolized as V) that creates an electric field.
This electric field exerts a force on free charges, causing current to flow. It's also important to note that the current flowing through a substance is directly proportional to the applied voltage, according to Ohm's Law, established by Georg Simon Ohm.