Bell knew that he could make sound by energizing a speaker.  But how could a human voice make electricity? Somehow he had to figure out how to convert human speech to electrical energy.

Look at this experiment to see the basics of the design:

The question for Bell was, how could he move a magnet from merely the impact of sound waves?  In theory, he made this design:

1: The sending cup

2: A magnet attached to the bottom of the cup 

3: A coil 

4: connecting wire

5: Coil

6: Magnet and Receiving cup

We can reproduce his system with two regular speakers.  Follow this activity to reproduce the sound powered telephone system.

Materials Required

• two small speakers with attached wires 

• two paper cups (The size of the bottom of the cup should be the diameter of the small speaker)

• glue or tape

• Scissors

• Paired, long wires


1. Cut a hole in the bottoms of two cups.

2. Glue or tape a speaker to the bottom of the cup

3. Repeat the process with the other cup and connect the wires so you have a system that looks like this:  

You can separate the sender/receivers by using a set of paired longer wire. You can use the paired  colored wires in your materials and strip he insulation off the ends using the wire stripper. (By the way, the blue wire in your materials is from telephone cable removed from the building where I am located. The IT folks were upgrading so I asked if I could have the removed wire.)

4. Now test the system. Speak into one cup while your friend listens in to the other.

PLEASE RESPOND:  What are your results from this simple sound-powered system?

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