MAGNETISM AND ELECTRICITY 183 



ness and precision, galvanometers constructed to register up 

 to 1100 F. can be used only in a horizontal position on a 

 table or in a bracket. This limited use is also common to 

 galvanometers constructed to register higher temperatures 

 up to 2900 C., and to those designed to register very low 

 temperatures. 



Questions 



1. What is magnetism? 



2. Explain the difference between a natural and an artificial 

 magnet. 



3. Describe the shapes of magnets. 



4. Explain the expressions: "magnetic flux/' "lines of force," 

 "magnetic field." 



5. What is a mariner's compass? 



6. What is the relation between electricity and magnetism? 



7. What is electromagnetic force? Name some of the indus- 

 trial uses of this principle. 



8. Describe an electric bell. 



9. What is a simple voltaic cell? 



10. Describe the chemical means of generating electricity. 



11. What is electrolysis? Is it an important industrial process? 



12. Describe some of the most common battery cells. 



13. What is a dry cell? 



14. Explain the use of a storage battery. 



15. What is an electric pyrometer? Describe it. 



16. What is a galvanometer? 



17. What is an ammeter? Voltmeter? 



18. In what units is electricity measured? 



19. Explain Ohm's Law. 



20. Describe the arrangement of electrical apparatus, 



