======String Telephone======


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**Materials: **{{$demo.materials_description}}\\
**Difficulty: **{{$demo.difficulty_description}}\\
**Safety: **{{$demo.safety_description}}\\
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**Categories:** {{$demo.categories}}
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**Alternative titles:** Talking Cups
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====Summary====                   
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====Procedure====  
  - Use a push pin to poke a small hole in the bottom of two paper cups (adult supervision recommended).  
  - Cut a length of string (10 feet or longer) and thread it through both holes.  
  - Tie a paper clip to each end of the string or tie a knot inside the cups to keep it from slipping out.  
  - Have two people each hold a cup and walk apart until the string is pulled tight.  
  - Speak clearly into one cup while the other person listens through the second cup.



====Links==== 
String Telephones - TeachEngineering: 
{{youtube>JWB_-wevjSY?}}\\

📄 Make a String Telephone - Virginia 4-H: [[https://ext.vt.edu/content/dam/ext_vt_edu/topics/4h-youth/makers/files/ww1-telephones.pdf]]\\


====Variations====
  * Use fishing line, yarn, or embroidery thread instead of string.  
  * Try different cup materials (plastic, paper, metal) or cup sizes.  
  * Make a three-way call by attaching multiple strings to one cup.  
  * Test what happens when the string is slack or when you touch it during transmission.



====Safety Precautions====
  * Adult supervision required when using push pins or scissors.  
  * Do not pull the string too tightly—it may snap back.




====Questions to Consider====
  * What happens when the string is tight versus loose? Why?  
  * How does sound travel from one cup to the other? (Through vibrations in the string.)  
  * What happens if you hold the string while someone is talking? Why is it like muting the line?  
  * How does this experiment compare to how landline telephones or cell phones transmit sound?  
  * Which materials made the clearest string telephone? Why do you think that is?