Concept:A loudspeaker turns a varying electrical signal into sound by producing an alternating magnetic force on its speech coil.
Explanation:The speech coil receives a varying current signal, not a steady one.
This current creates a magnetic field that interacts with the permanent magnet.
As the current reverses direction, the magnetic force on the coil also reverses.
Therefore, the force is alternating, not uni-directional.
So the false statement is that the magnetic force is uni-directional.
Answer:D. The magnetic force on the speech coil is uni-directional.