Final answer:
In a circuit, the source is where energy is stored, such as in a battery or solar cell, and is essential for driving current by creating a potential difference and an electric field.
Step-by-step explanation:
The source in a circuit is where the energy is stored and provided to the circuit; this includes components such as batteries, generators, solar cells, and other voltage sources. A source is fundamental in driving current by creating a potential difference across the circuit, which establishes an electric field. This electric field then exerts force on the free charges present in the conductors, leading to the flow of current. Moreover, the resistance offered by various circuit elements, which depends on the material's resistivity, will affect the amount of current that flows through the circuit. All of this is encompassed by Ohm's Law, which states that the current (I) is directly proportional to the voltage (V) and inversely proportional to the resistance (R) in a circuit.