MAGNETS. 195 



EXERCISES AND QUESTIONS. 



1. (a.) What is a magnetic pole? (b.) A magnetic equator! 

 (c.) How does a magnet behave toward soft iron? (d.) How does 

 soft iron behave toward a magnet ? 



2. (a.) State carefully the various effects which one magnet may 

 exert upon a second magnet. (&.) Generalize these observed facts 

 into a law. 



3. (a.) Give a theory of magnetism. (&.) State its merits and (c.) 

 its demerits. 



4. (a.) Given a bar magnet, how would you determine the sign of 

 either of its poles? (&.) What is a diamagnetic substance ? 



5. (a.) Illustrate magnetic induction, (b.) Explain it. (c.) If a 

 magnetic needle be freely suspended from its centre of gravity, 

 what position will it assume? 



6. (a.) Do you think that the earth is a magnet ? (&.) Give a good 

 reason for your answer, (c.) Do the magnetic and geographical 

 meridians ever coincide ? (d.) Do they always coincide ? (e.) If 

 they do not coincide, what name would you give to their difference 

 in direction ? 



7. (a.) Does the magnetic attraction of the earth upon a ship's 

 compass tend to float the ship northward ? (b.) If so, why ? If not, 

 why not ? (c.) What is an armature, and (d.) what is it good for ? 



8. (a.) State and illustrate the second law of motion, (b.) State 

 and illustrate the law of universal gravitation, (c.) A body falls to 

 the ground from rest in 11 seconds ; what is the space passed over ? 



Recapitulation. In this section we have considered 

 Natural and Artificial Magnets; Magnetic 

 Poles ; the Attraction of a Magnet for Ordi- 

 nary Iron ; the Law of Magnets ; a Broken 

 Magnet ; the theory of Magnetic Fluids and its 

 .value ; Magnetic and Diamagnetic substances ; 

 magnetic Induction with illustrations; magnetic 

 Curves ; magnetic Needles ; the Earth as a 

 Magnet, and its inductive influence; the Nomen- 

 clature of magnetic poles ; Dip and Variation ; 

 how to Make Magnets and how to Keep them. 



