Final answer:
The symbol E usually represents electromotive force (emf) in the context of electric circuits, and also electric field strength in the context of electric fields. It is a measure of the energy supplied by a source per unit charge, and it is expressed in volts.
Step-by-step explanation:
The symbol E commonly represents electromotive force, which is the electric potential created by any source of electric energy in a circuit. Electromotive force (emf) measures the energy supplied by a battery or generator per coulomb of charge passing through it, and it is also symbolized by the letter 'E'. It is important to understand that electromotive force isn't an actual force; rather, it's a potential difference which can enable an electric current to flow in a circuit.
Additionally, in the context of electric fields, the letter 'E' can denote the electric field strength, which is the force per unit charge exerted on a small positive test charge in an electric field. The strength of the electric field is expressed in units of Newtons per Coulomb (N/C).
When calculating electric potential, it's essential to understand that it represents the work per unit charge required to move a charge within an electric field. Electric potential energy is the energy a charge possesses by virtue of its position in the field.