Question

Which of the following devices does not convert electrical energy into sound energy?
A) A loudspeaker
B) A microphone
C) A buzzer
D) An electric bell

Answer 1

Hint: Conversion of energy means conversion of input energy to output energy. Try and recognize where input is electrical and output is sound energy. Generally the devices delivering sound are sound output devices. If a device delivers light energy or heat energy, its output would be light or heat.

Complete step by step answer:
In the question we are required to opt out the one electronic device that does not convert electrical energy to sound energy. In this case. The input energy is electrical energy and output energy is sound energy.
In a loudspeaker alternating current is supplied to the loudspeaker and it produces sound waves by repeatedly changing the current direction in the coil and thus repeatedly changing the magnetic field inside the speaker to cause pressure variations in the air and create sound waves.
The microphone uses the opposite effect from the loudspeaker, that is it uses altering air pressure to generate magnetic fields in a coil connected in a closed circuit and induce flow of current.
The buzzer and an electric bell also uses electrical energy as input and they have slightly different circuit designs to produce different sound effects. But the output energy is released in the form of sound waves.

So, the answer is (B), a microphone because it does not convert electrical energy to sound energy rather it converts sound energy to electrical energy.

Note: You don’t have to be an expert in electronics to solve these questions. If the input is in some form of energy and the output is in another form, just compare the options with the provided data and opt the odd one out. In this case, three options had electrical input and sound output.
Some other relatable examples,
i) A generator uses mechanical input and produces electrical output
ii) A bulb uses electrical input and produces light energy.
iii) A motor uses electrical input and produces mechanical output.