USING ELECTRICITY ABOUT THE HOME 



25J 



Powers, Neuner, and Bruner, Man's Control of His Environ- 

 ment, Unit 5 



Shilling, Tours through the World of Science, Tour 10 

 Van Buskirk and Smith, The Science of E^'eryday Life, 



Chap. 17 



Watkins and Bedell, General Science for Today, Chap. 24 

 Webb and Beauchamp, Science by Observation and Experi- 

 ment, Unit 5 (part) 



Wood and Carpenter, Our Environment: How We Use and 

 Control It, Topic 9 



Special references 



Lunt, Everyday Electricity 

 Meister, Magnetism and Electricity 

 Darrow, Masters of Science and Invention 

 Morgan, The Boy Electrician 

 Collins, The Book of Electricity 



WHAT YOU SHOULD AIM TO ACQUIRE FROM 

 THIS STUDY 



1. Understand thoroughly the principle of securing 

 electrical energy from mechanical energy. 



2. Know the contributions of Faraday and Edison to 

 the development of the modern electric generator. 



3. Have a knowledge of how modern electrical plants 

 secure the mechanical energy needed to turn the 

 dynamos. 



4. Understand the importance of conserving our pres- 

 ent sources of energy such as coal, oil, and water 

 power. 



5. Know the two types of electric current and what 

 they are used for. 



6. Understand the principle of the transformer. 



TEST OF MASTERY OF THE TOPIC 

 In your notebook complete the statements. 

 1. The is the moving part of an electric generator. 



2. An electric current is produced whenever a 



moves in a 



3. In the magneto-generator the magnetic field is furn- 

 ished by magnets. 



4. If the armature of a generator is turned , more 



is produced. 



5. Generators equipped with commutators give (alter- 

 nating, direct) current. 



6. current is produced in the of all electric 



generators. 



7. All batteries give (alternating, direct) current. 



8. Magneto generators are sometimes used to . 



9. discovered the principle of the electric genera- 

 tor. 



10. built the first electric generator. 



11. The amount of electrical energy produced by a genera- 

 tor depends upon the number of , the rate of , and 



the number of 



12. Steam or may be used to turn the of a 



generator in the field. 



13. A direct current always flows 



14. The of a dynamo take the current from the com- 

 mutator. 



15. The telephone magneto furnishes current to the 



outside circuit. 



16. Any generator applies the discovery made by 



17. Transformers are used to . or electrical . 



18. Transformers are used only with current.. 



19. If the is raised by a transformer there are more 



turns in the coil than in the coil. 



20. When the voltage is raised in a transformer the 



is lowered. This line losses because they are caused 



mostly from of the wires, and this depends upon the 



number of flowing through them. 



21. Electricity from the generating station is reduced 

 in at a point in the transmitting system called a . 



22. Most electrical devices used in the home are designed 

 to operate at volts. 



TOPIC 4. USING ELECTRICITY ABOUT THE HOME 



SUGGESTED PROBLEMS AND QUESTIONS 



1. What are electric fuses for, and how are they 

 replaced? 



2. How do electric heating devices work? 



3. How do electric lights work? 



4. How do electric motors work ? 



SUGGESTIONS AND HELPS FOR STUDY 



1. Carefully study the problems to see if you are 

 interested in them. 



2. Get as much experience in replacing fuses and 

 in observing electrical heating devices, motors, and 

 lights as you can. This can be done both at home and 

 at school. 



3. In this study the following new words and 

 phrases may be encountered: 



insulator a substance which will not conduct the elec- 

 tric current. 



resistance a retarding experienced by the electric cur- 

 rent as it flows through various conductors ; from this 

 resistance heat energy is developed. 



nichrome an alloy of nickel, chromium, and iron which 

 has a high resistance for the electric current. This is 

 often used in the heating element of toasters, electric 

 irons, etc. 



EXPERIMENTS OR DEMONSTRATIONS WHICH WILL 

 HELP ANSWER THE PROBLEM QUESTIONS 1 



Experiment 156. What happens when a fuse burns 

 out? 



Make a fuse board as shown in Figure 401, driving the 

 nails about one inch apart. Cut a strip of tin foil wrapper 

 secured from a candy bar and attach it to the nails. Con- 

 nect the wires to the nails as illustrated and finally to the 

 battery through a push button or switch. Allow current from 

 the dry cell to flow and observe what happens. Hold a small 

 piece of the tin foil in a match flame. Examine new and 

 burned-out fuses. Secure a piece of fuse wire from an un- 



1 See workbook, p. 91. 





