Figure 14 shows a sound wave incident on the diaphragm of a moving-coil microphone. The inside of the microphone includes a small coil of wire and a magnet. Explain why the sound waves have an effect on the electric circuit.

A moving-coil microphone converts sound energy into electrical energy using the principle of electromagnetic induction. 1. **Vibration:** The incoming sound waves consist of compressions and rarefactions, which are pressure variations. These variations exert a changing force on the diaphragm, causing it to vibrate back and forth. 2. **Coil Movement:** Since the coil of wire is attached to the diaphragm, it vibrates with the same pattern as the sound wave. 3. **Electromagnetic Induction:** The microphone contains a permanent magnet that creates a magnetic field. As the coil moves back and forth within this field, the wire cuts through the magnetic field lines. 4. **Induced Current:** This cutting of field lines induces a potential difference (voltage) across the ends of the coil. Because the coil is part of a complete circuit, this potential difference drives an alternating current that mirrors the vibrations of the sound wave. This electrical signal can then be amplified and recorded.