Definition
The loss of polarization in a generator's field, in which the residual magnetism in the field frame weakens or reverses. Without proper residual magnetism, the generator cannot build up voltage when it begins to turn, and it must be repolarized (flashed) to restore correct field polarity before it will produce output.
Plain English
A generator relies on a small amount of leftover magnetism in its frame to start producing electricity. Depolarization is when that leftover magnetism gets weak or backwards, so the generator can't get going on its own and has to be reset.
Context Anchor
Seen in aircraft electrical-system and battery discussions, especially when describing how a cell maintains voltage during use.
Derivation
From 'de-' (to remove or reverse) and 'polarization' (the establishment of a magnetic polarity, i.e., a north and south pole). So depolarization literally means removing or reversing the magnetic polarity that the generator depends on.
Why Pilots Care
A depolarized generator won't charge the battery or power the electrical system, even though it appears mechanically fine. Knowing the term helps a pilot understand why a mechanic may need to 'flash the field' to bring the generator back online.
Analogy
It is like clearing a clog from a small drain. The drain was not gone, but the blockage kept it from working normally.
Grounding Statement
Picture a battery cell whose chemical action is being blocked at one internal plate; depolarization removes that blocking effect so the cell can keep producing voltage.
Intuition Check
Depolarization does not mean reversing the battery terminals or making the battery have “no positive and negative.” It means removing an internal effect that is reducing the cell’s ability to deliver voltage.
Example Sentence 1
After the generator was installed backwards on the test bench, depolarization left it unable to produce output until the mechanic flashed the field.
Example Sentence 2
After extended use, the battery showed reduced output until depolarization was addressed during servicing.