What is the principle of operation based on: a) an electric motor; b) pointer electrical measuring instruments

What is the principle of operation based on: a) an electric motor; b) pointer electrical measuring instruments of the magnetoelectric system; c) dynamics?

a) the principle of operation of an electric motor is based on the action of a magnetic field on a frame with a current. b) the operation of electric pointer instruments is based on the phenomenon of rotation of a frame with a current in a magnetic field. c) the effect of the speakers is based on the phenomenon of the emergence of forces tending to draw the frame with current into the region of a stronger magnetic field.

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