Aircraft Electrical Systems How does the magnetic brake used to stop rotation of an electric motor armature operate? a. Centrifugal force releases a rotating brake cog from a stationary notch when the armature reaches a certain speed and magnetic force re-engages the cog when the electrical power is turned off. b. A friction brake is applied by a magnet and released by a spring. c. A friction brake is applied by a spring and released by a magnet.