Applied Science - Built Environment (4)
Pre Lab

Students use a worksheet to study Morse code

OBJECTIVES:

• Investigating how a telegraph works.
• Exploring communications.

VOCABULARY:

• telegraph
• transmit

MATERIALS:  

• worksheet
• telegraph model 

BACKGROUND:

The telegraph is one of the earliest uses of the electromagnet. This unit is in "built environment" because the series of experiments that are discussed below have changed how humans interact. Emphasize that these are relatively recent developments. Telegraphy is a communication system using the medium of electromagnetic phenomena. Information is transmitted in written, printed, or pictorial form. Facsimile Transmission (FAX) is a form of telegraphy. The use of FAX machines have increased within the last decade years due to improved telephone "fiber optic" wires. The fax machine converts the image into light pulses, which is send through fiber optic wire. The receiving fax machine then decodes the pulses of light into a copy of the document on a photosensitive paper. The facsimile was first outlined in a British patent of Alexander Bain in 1843. The high information density that can be carried telegraphically and the importance of the printed record provides a service that cannot be given by the telephone.

In England in 1747, Sir William Watson, demonstrated that an electric current could be transmitted through wire. However, Samuel Morse (1791 - 1872) is credited with the invention of the useable telegraph and the Morse code. This invention helped communication developed into the industry that is used today. In 1843, the first telegraph in the U.S. was installed from Baltimore to Washington. The first message was "What hath God Wrought". The Morse code is a series a dashes (long) and dots (short) signals, that basically represents a break in a circuit. The evolution of the telegraph technology we have today included many different designs. Impress upon your students that even after an invention is made, the product must be constantly revised to create a better product.

Another inventor, Guglielmo Marconi (1874 -1937), was the inventor of radiotelegraphy. In 1900, Marconi filed his famous patent No. 7777 which used a transmitter to transmit signals without a wire. It was commonly called the "wireless" telegraph. It concentrated electrical energy into a beam, so it could travel over long distances. This invention allowed transmission of information over long distances without expensive cable. Europe could now send messages to America. The communication revolution began.

PROCEDURE:

1. The Morse Code is enclosed on the worksheet. Have students create some messages on a paper. The elementary telegraph circuit consists of a key that makes and breaks the connection between a source of current and the line according to the signaling code and the pulses of current passing through the line.
     
2. Use the information below to create a model of a telegraph. Demonstrate how it is used. It is difficult for students to make their own because of the use of the electromagnetic, but the demonstration will help students recognize the use of the electromagnet.

MATERIALS:
steel nail (about 8 cm long)
300 cm of insulated copper wire
battery with total of 6 volts
7 metal (steel) thumbtack

DIRECTIONS:  
Make an electromagnet from the nail by winding wire around the nail. Hammer this nail with the wire around it into the center of a soft piece of wood, about 10 cm by 25 cm. Fasten the two wires that come from the electromagnet to the board by means of thumbtacks as shown in the diagram. Push another thumbtack about 3 mm from one edge of a strip of cardboard that measures about 4 cm by 8 cm, and bend the pin over to keep it from falling out. Fasten the other end of this cardboard strip with another thumbtack to a piece of wood which is about 3 mm higher than the head of the nail. Fasten this smaller piece of wood (which now has the cardboard with the tack on it) to the larger strip so that the head of the independent thumb tack faces the nail head and is about 3 cm above it. The telegraph sounder is complete.

Connect the switch and battery to the telegraph sounder. When you press the switch, you close the circuit and allow current to flow from the battery through the electromagnet. The thumbtack, as it is made of magnetic material will now be attracted to the head of the nail. When this happens, you will hear a click. As soon as you release the switch, the thumbtack will snap back. Push the switch once more, and the tack will come down again with a click. The telegraph is now working!

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