Question

A typical audio speaker, such as that in a radio, consists of a permanent magnet, a coil of wire, and a movable speaker cone. The coil of wire is connected electrically to the radio's amplifier so that the radio controls how much current flows through the coil. The coil is attached to the speaker cone so that if the coil moves, the speaker cone moves and creates sound waves in the air.

A. If the radio reverses the direction of current through the coil 500 times each second (250 complete cycles each second, or 250 Hz), what will happen to the speaker cone?

Answer 1

If the direction of current through an audio speaker's coil is reversed 500 times a second, the speaker cone will vibrate at a frequency of 250 Hz, creating sound waves through air pressure changes within the audible range for humans.

Step-by-step explanation:

When the direction of current through the coil of an audio speaker is reversed 500 times each second, meaning that there are 250 complete cycles per second or 250 Hz, the speaker cone will also move back and forth 500 times each second. The rapid movement of the coil generates a corresponding vibration in the speaker cone which then translates into variations in air pressure - these are sound waves.

That is, the cone of a speaker vibrates to create small changes in the pressure of the air, leading to the production of sound. As a result, the speaker cone will produce a sound at a frequency of 250 Hz, which is within the audible range for human hearing. The alternating current flowing through the coil creates a changing magnetic field that interacts with the permanent magnet in the speaker, causing the coil, and thus the cone attached to it, to move in and out.