According to the rule of thumb, how does active power flow relate to the power angle?

Active power flow is closely related to the power angle, which represents the phase difference between voltage and current in an electrical system. The rule of thumb indicates that as the power angle increases, the active power flow tends to increase. This relationship is derived from the principles of synchronous generators and the operation of transmission lines.

When considering the concept of power flow in electrical systems, the 'uphill' or 'downhill' terminology describes how the flow of active power is influenced by the difference in voltage magnitude between two points—one being the sending end and the other the receiving end. As the power angle increases, it typically signifies an increase in the transmission line loading condition, which indicates that power is flowing from a region of higher potential (voltage) to a lower potential, effectively 'downhill.'

Choosing the option that states power flows downhill with an increasing power angle is grounded in this understood behavior of active power in a power system. As the angle between the voltage sources widens, the driving force (or resultant difference) pushing the active power through the line becomes more pronounced, leading to a greater flow of energy 'downhill,' where it is needed.

This understanding reflects fundamental electrical engineering principles, making it clear why this choice accurately describes the