Simple Telephone

So friends, today we will make a simple telephone and learn something about sound. 
 
Accessories: 2 Match boxes, 2-3 meter medium thickness thread, 2 match stick.

Method:
Step 1: Make a hole in center of an open match box. .
Step 2: Tied a used match stick using thread and pass the other end through the hole of paper cup.
Step 3: pass other end of a thread into another open match box and tied it with another used match stick over there.

Application: It’s a simple telephone model. You can play it with your friend.

Advance version: We will use cylindrical metal box instead of paper cup and thin copper wire instead of thread. We can avoid noise and have better voice quality. Why better voice quality? Metal has high thermal and electrical conductivities. A copper cable provides better elasticity also when stretched at both end, compare to a thread.

Theory: Now let’s know some theory, how it works? We know, that sound needs an elastic medium to propagate. Air is such medium, in gas form. Here the thread and copper wire is such medium in solid form. The medium vibrates along with sound waves.

Limitations: Of course, it works point to point, for you and your friend. It is not for long distance call, as the wave signal travelling in thread or copper wire is weakens.
Future Scope:  The gramophone/phonograph has a metal cone, which acts as amplifier. May be, we can use that instead of paper cup cylinder. 
 
Questions:
Why astronauts use cordless phones to talk, even they are standing just nearby?
Why we can hear sound from conch shell (SHANKH)?
Why we cannot hear sound from empty conch shell in sound-proof cabin?
How can you talk across a glass wall, without using sound?
Do you know answers? Yes? Immediately write in comments section. No? Wait for next episode.
 
We will re-visit the telephone again,sometime later. Our next telephone will be wireless. No thread, no copper cable, yet simple. Yes, you can make it and use it. We will learn a new scientific theory behind our wireless telephone.
So stay tune to make science learning as fun, to this blog E-Science Center.

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