Definition
In an alternating current (AC) circuit containing inductance or capacitance, the component of current that is 90 degrees out of phase with the voltage. Reactive current does no useful work in the circuit; it flows back and forth between the source and the reactive component (the inductor or capacitor) as energy is alternately stored in and returned from the magnetic or electric field.
Plain English
The part of an AC current that sloshes back and forth between the power source and components like coils or capacitors without actually doing any work. It carries energy out and brings it right back, instead of turning it into useful output like light, heat, or motion.
Context Anchor
Seen in aircraft electrical-system discussions involving alternating-current equipment, inverters, generators, motors, and electrical-load troubleshooting.
Derivation
From 'react,' meaning to push back or respond. In AC circuits, inductors and capacitors react against changes in current and voltage by storing and releasing energy, rather than consuming it. The current associated with that pushing back is called reactive.
Why Pilots Care
Reactive current adds load to generators and wiring without producing useful work, which affects how electrical systems are sized and how power factor is managed. Pilots and technicians dealing with AC systems (such as those on larger aircraft) need to understand that not all current shown on a meter is doing work.
Grounding Statement
In an AC circuit, a coil or capacitor can take in energy for a moment and then give it back, creating a back-and-forth part of the current.
Intuition Check
Reactive does not mean the current is responding to a pilot action. Here it means current caused by stored electrical energy being returned to the circuit. Current does not mean “present” or “up to date” here. It means the flow of electricity.
Example Sentence 1
Because the motor's windings are highly inductive, a large reactive current flows in the circuit even though the motor is lightly loaded.
Example Sentence 2
Excess reactive current can reduce efficiency without adding to the power available for avionics.