Normal polarity is for the power to normally go from positive to negative, reverse polartity is to change the positive to a negative and the negative to a positive so the power goes the other way.
It would indicate that the length of time between reversals is not predictable.
It depends on the context. In a.c. circuits, 'reverse polarity' describes a situation in which a device, such as a socket outlet, is wrongly wired -with the line and neutral conductors interchanged.
Improperly wired receptacle is the normal cause.
time scale
It was reversed 65 million years ago. This is an approximate answer.
because they showed alternating bands of normal and reversed polarity.
In a normal distribution system, one wire is always connected to earth. Reverse polarity occurs when the live and neutral conductors on a system become reversed or 'swapped over'. It's a very dangerous situation with serious safety implications.
Mid-Atlantic ridge
I need help
Normal polarity.
Gilbert reversal epoch
Oceanic crust on both sides ofthe ridge shows matching patterns of reversed and normal magnetic polarity