PROBLEM: How can you transmit signals using a circuit?

PREDICTION:

EXERCISE I:
MAKING A SWITCH
MATERIALS: 1 metal tack, 1 metal push pin, 3 paper clip, thick cardboard or piece of wood

PROCEDURE: Use a tack that is only metal. Put two paper clips and one push pin on one side of the base (wood or thick cardboard) as in diagram. Open up the paper clips before you attach them. Place the other paper clip down on the opposite side with the metal tack. Bend the paper clip that will make contact with the tack so that you have to force it down to make a connection (see diagram). You now have a switch.

EXERCISE II:
PROCEDURE: Set up equipment to make a light telegraph as in the diagram below. Make sure the circuit is complete. Note that this is not a "real" telegraph. A telegraph is made of an electromagnet so it can intensify the signals sent over long distances.

Practice the letters of the Morse Code so you can recognize a dot (quick pulse) and a dash (long pulse), Test your partner.

Practice sending the following words. Write it first in Morse Code.

EXERCISE 3. Write a message in Morse Code. Send it to your neighbor. Have your neighbor send you a message. 
The message is:

 

In Morse Code:

 

My neighbor's message is:

 

CONCLUSIONS: What is the principle of a telegraph?