Man's physical universe

xanabras

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538 MAGNKTISM AND I:LI{CTRIC1T\

STUDY QUESTIONS

1. How did Hertz prove that electromagnetic waves would travel without wires?

2. What is the principle of the coherer tube?

3. Gi\e a brief discussion of Marconi and his work.

4. What contribution did Edison make to the radio?

5. Explain what is meant by tuning.

6. Explain the action of the vacuum tube. For what purposes may vacuum

tubes be used?

7. How are electromagnetic waves produced?

8. Describe the different types of vacuum tubes, and give the use of each.

9. What is the function of the ordinary radio receiving tube?

10. Discuss the social consequences of the development of the radio.

11. What is the principle of microphones?

12. What is the principle of the dynamic loud-speaker?

13. How does frequency modulation differ from ordinary radio broadcasting?

14. What are the advantages and disadvantages of frequency modulation?

15. What is meant by thermionic emission?

16. Point out the fallacy in the following e.xample of reasoning: "Egyptologist:

There is nothing new under the sun. Recent excavations in Eg>'pt have

brought to light very old wires which make it highly probable that telephones

were already used by the Egyptians in the time of Pharaoh.

" Assyriologist: The Assyrians and Babylonians were even more advanced

than that. No wire has ever been discovered during excavations in Mesopotamia.

This makes it highly probable that the ancient Assyrians and Babylonians

were already familiar with wireless." ^

p. 23.

'

A. Wolf, Exercises in Logic and Scientific Method, George Allen and Unwin, Ltd., 1933,

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