Answer:
C. a current that rapidly switches direction
Explanation:
An audio speaker is an electronic device that converts electrical signals into sound energy (waves). The alternating current flowing into the audio speaker is typically used to generate sound waves.
Hence, what causes the poles of the electromagnet in an audio speaker to repeatedly switch directions is due to a current that rapidly switches direction. The electromagnet is placed in a position where it experiences a constant magnetic field as a result of the presence of a permanent magnet. Like every magnet, the electromagnet and the permanent magnet interact with each other; opposite sides attract while like sides attract. This interaction generates a force, causing the alternating current to constantly reverse the poles of the electromagnet in an audio speaker to repeatedly switch directions.
