What is the cause of current flow in an electrical circuit?

Current flow in an electrical circuit is fundamentally driven by a voltage difference between two points. This voltage, often referred to as electrical potential difference, creates an electric field that pushes charged particles, typically electrons, through the circuit. The greater the voltage difference, the greater the driving force for current to flow, assuming the circuit has a closed path and load.

A closed loop is indeed necessary for current to flow, as it allows charge to move continuously through the circuit. However, without a voltage difference, there would be no motive force to drive that current.

While a magnetic field can influence the movement of charges, typically through induction, it is not the primary cause of current flow in a standard circuit. Resistance is a property of the circuit that opposes current flow, rather than causing it. Thus, the key factor that initiates current flow is the voltage difference.