PROBLEMS AND EXERCISES. 411 



PROBLEMS AND EXERCISES. 



QUESTIONS ON CHAPTER I. 



1. From what is the word " electricity" derived? 



2. Name some of the different methods of producing electri- 

 fication. 



3. A body is charged so feebly that its' electrification will not 

 perceptibly move the leaves of a gold-leaf electroscope. Can 

 you suggest any means of ascertaining whether the charge of the 

 body is positive or negative ? 



4. Describe an experiment to prove that moistened thread^ 

 conducts electricity better than dry thread. 



v 



5. Why do we regard the two electric charges produced 

 simultaneously by rubbing two bodies together as being of 

 opposite kinds ? 



6. Explain the action of the electrophorus. Can you suggest 

 any means for accomplishing by a rotatory motion the operations 

 of lifting up and down the cover of the instrument so as to obtain 

 a continuous supply instead of an intermittent one. 



7. Explain the Torsion Balance, and how it can be used to 

 investigate the laws of the distribution of electricity. 



8. Two small balls are charged respectively with + 24 and 

 8 units of electricity. With what force will they attract one 

 another when placed at a distance of 4 centimetres from one 

 another? Am. 12 dynes. 



Q. If these two balls are then made to touch for an instant 



