Question

An electric speaker produces sound if a constant current is made to pass through its coil.

• A. An electromagnet to rotate the armature
• B. Effectively large number of turns of conducting wire in the current carrying coil

Answer 1

The correct option is B

Effectively large number of turns of conducting wire in the current carrying coil

Sound is produced by a speaker when its diaphragm vibrates. When a constant current passes through the speaker, there is no change in the magnetic flux through the coil and thus no force is produced and the diaphragm does not vibrate, so the sound is not produced.