Final answer:
The source of electromotive force (emf) is a voltage source's electrical energy capable of maintaining a constant potential difference, even when no current is flowing. It includes internal resistance and despite its name, it is not a force but a potential that provides energy per unit charge to charges in a circuit. Examples include batteries and generators.
Step-by-step explanation:
Understanding Electromotive Force (emf)
The source of electromotive force (emf) is an electrical energy source within voltage sources, characterized by its ability to maintain a constant potential difference. This constant potential difference is what is known as emf. The misconception that emf is a force comes from its historical name, but it is actually a potential. Devices that create emf include batteries, where a chemical reaction occurs to maintain a potential difference, and generators, where mechanical energy is converted into electrical energy. The term 'emf' denotes the work done per unit charge to produce a constant potential difference across a voltage source, typically when no current is flowing. Additionally, emf includes an internal resistance, reducing the output voltage when a current is drawn.
Furthermore, an induced electromotive force occurs when there is a change in the magnetic field, such as in a coil, leading to the production of an electrical potential, as explained by Faraday's law of induction. The common unit of emf is volts, indicating that it represents energy per unit charge imparted by the source. Thus, while emf is referred to as 'force,' it is better conceptualized as the energy provided to push charges through a circuit.