Q. Which of the following phenomena is utilised in the construction of mouth piece of a telephone now a days?
A) Thermo electric effect
B) Photo electric effect
C) Change of resistance with pressure
D) Electromagnetic induction
Explanation
(c) In the construction of mouth piece of a telephone, we use the phenomenon of change of resistance with pressure (of sound waves).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.