CHAPTER II 

 QUANTITY AND CAPACITY, CONDENSERS 



1. A current of 5 amperes flows for one-half hour; how many 

 coulombs are passed? To what e.m.f. would this raise a 20-micro- 

 farad condenser? A 50-microfarad condenser is charged to 2000 

 volts; how long would this condenser maintain a current of one 

 ampere if closed through an outside circuit? (2 min.) 



2. An electric motor takes 1 kilowatt at 200 volts. How many 

 coulombs will it use in 2 hours? How many if the voltage be 500 

 and the power the same? (2 min.) 



3. How many coulombs and how many watt-hours are ropn-- 

 sented by the charge in a 100-microfarad condenser on a 10,000- 

 volt circuit? What will each of these become if the voltage is 

 doubled? (4 min.) 



4. To what voltage will 5 coulombs charge a 1-microfarad con- 

 denser? A 100-microfarad condenser? (1 min.) 



5. How long would it take to charge a 10-microfarad condenser 

 on a 50,000-volt circuit, if the average current were 2 amperes? 

 How long to charge with the same current a 100-microfarad con- 

 denser on a 100-volt circuit? (2 min.) 



6. What would be the capacity in microfarads of a condenser 

 which would require 2000 volts to bring to a charge of 1 coulomb? 

 (J min.) 



7. What capacity would be necessary to run a 25-watt tungsten 

 lamp for 5 minutes at 100 volts? If a 2-microfarad condenser 

 costs 90 cents what would the above cost? (3 min.) 



8. What voltage would be required to charge a 50-microfarad 

 condenser with one coulomb of electricity? (1 min.) 



9. In 0.02 second the charge in a condenser changes from 0.283 

 to 0.231 coulomb; required the average current flowing. (\ min) 



10. A 10-microfarad condenser shows a drop in voltage from 

 3000 to 1500 in 0.03 second; required the average current. (/ min.) 



11. Three condensers each having a capacity of 30 microfarads 

 are in parallel. What is the combined capacity? What would 

 be the capacity if they were in series? ( min.) 



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