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A circle containing the letter M, marking an electric motor.
Also known as: Circle with an M, Electric motor symbol, M in a circle
A circle with an M inside marks an electric motor. It belongs to a family of lettered circles used across schematics — G for generator, V for voltmeter, A for ammeter — in which the circle means a machine or instrument and the letter says which.
Marks an electric motor: a machine converting electrical energy into rotary mechanical motion.
Contexts: Electrical equipment
Belongs to a convention of lettered circles in which the circle denotes a rotating machine or an instrument and the enclosed letter identifies which — M for motor, G for generator, V for voltmeter, A for ammeter.
Contexts: Electrical equipment
Is drawn identically to the generator symbol but for the letter, which reflects the underlying physics: many machines will run as either, depending on whether they are driven electrically or mechanically.
Contexts: Electrical equipment
Is a circle containing the letter M, and its counterpart is the same circle containing G for a generator — the two machines being the same device run in opposite directions. Where the distinction matters the type is added beside it, and where it does not, the circle alone is enough.
Contexts: Technical drawing, Electrical equipment
Related forms that are not treated as separate canonical symbols — see our variant rules.
Direct-current motor
The circle with M and a pair of straight lines, or the letters DC, marking a machine fed with direct current.
Alternating-current motor
The circle with M and a sine wave, marking a machine fed with alternating current. Three connections drawn to it make it three-phase.
A plain circle with a capital letter M standing upright at its centre.