The mouth piece of a telephone handset converts

Step 1: Analyze the question The question asks what energy conversion happens in the mouthpiece (the part you speak into) of a telephone handset.

Step 2: Explain the concept A telephone handset has two main parts:

• Mouthpiece (transmitter): a microphone. Your voice makes a diaphragm vibrate. These vibrations change the pressure on carbon granules (or the capacitance in modern types), which varies the electric current. This gives an electrical signal that matches your voice.
• Earpiece (receiver): a small loudspeaker. It changes the electrical signal back into sound.

Step 3: Work through the options

• A. Electrical to sound: this is the earpiece, not the mouthpiece. ❌
• B. Sound to electrical: this is what a microphone does, so it is the mouthpiece. ✅
• C. Sound to radiowave: this describes a radio transmitter, not a handset mouthpiece. ❌
• D. Radiowave to sound: this describes a radio receiver. ❌

Step 4: Answer The mouthpiece converts sound energy to electrical energy, which is option B.

Tip: Remember "Mouth = Mic = Makes electricity" and "Ear = Energy back to sound." Any input device such as a microphone converts sound to electrical energy, and any output device such as a loudspeaker converts electrical energy to sound.