Final answer:
The red wire in a loudspeaker cable carries an alternating signal.
Step-by-step explanation:
The red wire in a loudspeaker cable carries an alternating signal.
An alternating current (AC) changes direction periodically. In the case of a loudspeaker cable, the red wire carries the varying electrical signal that represents the sound being produced by the loudspeaker. This signal constantly fluctuates between positive and negative values as the speaker cone moves back and forth, creating sound waves.