Question

1. which of the following statements best summarizes how a speaker uses magnetism to produce an audible sound?

an electromagnet repels or attracts a permanent magnet to deflect a cone and displace air to produce sound waves.

when current is run through a permanent magnet, it produces a sound applicable to frequency.

the cone of the speaker funnels the electrical signal to the permanent magnet and produces a sound.

Explanation:

Analyze speaker components

A dynamic speaker consists of a permanent magnet, an electromagnet (voice coil), and a cone (diaphragm). The voice coil is attached to the cone and placed near the permanent magnet.

Apply electromagnetism principles

Using the Electromagnetism knowledge point, when an alternating electrical current flows through the voice coil, it generates a rapidly changing magnetic field. This field interacts with the static magnetic field of the permanent magnet.

Determine mechanical motion

The interaction between the two magnetic fields creates attractive and repulsive forces. These magnetic forces cause the voice coil (and the attached cone) to vibrate back and forth rapidly.

Relate motion to sound

The vibrating cone pushes and pulls the surrounding air, creating pressure waves (compressions and rarefactions) that travel through the air as audible sound waves.

Evaluate the given options

• Option 1: "An electromagnet repels or attracts a permanent magnet to deflect a cone and displace air to produce sound waves." This accurately describes the physical mechanism.
• Option 2: "When current is run through a permanent magnet..." This is incorrect because current runs through the voice coil (electromagnet), not the permanent magnet.
• Option 3: "The cone of the speaker funnels the electrical signal..." This is incorrect because the cone is a mechanical diaphragm, not an electrical conductor.

Answer:

• An electromagnet repels or attracts a permanent magnet to deflect a cone and displace air to produce sound waves. (Correct answer)
• When current is run through a permanent magnet, it produces a sound applicable to frequency.
• The cone of the speaker funnels the electrical signal to the permanent magnet and produces a sound.