The following statements about a loudspeaker are correct except?

Analyze the question: We need the statement about a loudspeaker that is NOT correct (the "except").

Concept: A moving-coil loudspeaker converts electrical signals into sound using the motor effect (a current-carrying conductor in a magnetic field experiences a force, given by F = BIL).

How it works:

1. A permanent magnet provides a steady radial magnetic field.
2. A sound signal (from a microphone or amplifier) is converted into an alternating, varying electrical current.
3. This current flows through the speech (voice) coil, which sits in the magnet's field.
4. The coil experiences a magnetic force, F = BIL.
5. Because the current alternates in direction, the force alternates too: the coil moves forward, then backward.
6. The coil is attached to a paper cone (diaphragm), so the cone vibrates and produces sound waves.

Check each option:

• A. Correct. A permanent magnet is present.
• B. Correct. The varying current signal enters the speech coil.
• C. Correct. The current in the coil in the magnet's field produces a magnetic force on the coil.
• D. Incorrect. The force is not uni-directional. Since the current alternates, the force reverses direction continually, making the coil and cone vibrate back and forth. If the force were in only one direction, the cone would just be pushed out and stay there, producing no sound waves.

Tip: For "loudspeaker" questions, remember "varying current → varying force → vibration → sound." A loudspeaker needs a force that changes direction. Also, don't confuse it with a DC motor, which uses a commutator to keep the rotation in one direction.