How can electricity help us communicate?

How can electricity help us communicate?

Materials needed

• Two small light sockets with bulbs 
• Two switches
• Lantern battery 
• Six 1 m (1 yd.) lengths of insulated copper wire.

Procedure

1. Use your materials to construct a circuit like the one in figure 8.22-1.
2. Press one switch. What happened?
3. Release the first switch and press the second one. What happened?
4. Press both switches at once.
5. Can you think of some use for a device like this?
6. If it is available, you could splice more wire into the circuit and take one switch and light into another room.

For problem solvers:

 look up the mores code in an encyclopedia. If you and a friend would care to learn the mores code, you could have a lot of fun sending messages to each other. Or you might prefer to create your own code. Set up your telegraph sets so that you can be in separate rooms, or in separate parts of the room, and make each other's light blink with your switch.

Teacher information

This is a variation of the telegraph. There are several ways to wire the circuit. This one is parallel. The original telegraph sets were wired in series so all keys to but one had to be closed and all messages went through all the sounders in the circuit. Telegraphs offices often followed the railroads and needed only one wire on the poles. The iron rails were used as the second or ground wire. The original telegraph, patented by Morse, used an electromagnet to attract a magnetic material (soft iron) and make a loud clicking sound. Telegraphers were trained to hear combinations of long and short "dots and dashes" to represent letters of the alphabet. This is called the mores code.
The completion of the transcontinental telegraph near the end of the civil war was extremely significant. For the first time, a message could travel across the nation in seconds rather than in weeks. The circuit above uses the electric light, which was not invented until much later.
In addition to the activity suggested in the "for problem solvers" section, your motivated students might enjoy designing and constructing a telegraph using electromagnets.