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# Science Project on “Making a Simple Telephone”, Project Experiment Topics on Light, Sound, Maths, Optical Illusion for Class 8, 9, 10 and 12 Students.

Making a Simple Telephone

Materials Required:

1. Two paper cups
2. A long piece of string
3. Toothpicks or wooden matches

To make a paper cup telephone, pierce a tiny hole at the bottom of one cup. Now insert one end of the string, through the bottom of the cup and pull it out from the open end of the cup. Tie the string to the middle of a match stick or a toothpick. Do likewise with the other end of the string inside the second cup.

The string will have to be long enough to allow two people to stand far apart, keeping the string taut.

You have to ensure that the match stick or the toothpick is firmly pressed against the bottom of each cup. Now, one person speaks into one cup while the other person holds the other cup to his ear and listens.

Vibrations created at the bottom of the cup by the speaker are transmitted by the taut string. The words can be heard distinctly by the second person listening at the other end of the taut string. In effect, the cup bottom functions like a diaphragm of a microphone or a speaker. The diaphragm vibrates when there is sound. The bottom of the paper cup reacts similarly.

In the paper cup telephone, vibrations are transmitted along the string. In an actual telephone, there is a conversion of the diaphragm’s vibrations into electrical impulses which in turn are sent through the wire. At the receiving end both the electrical impulses and the vibrations of the string are reconverted into sound after another diaphragm vibrates.