22 



ADVANCED ELECTRICITY AND MAGNETISM. 



coil 



15. The tangent galvanometer.* The tangent galvanometer 

 consists essentially of a circular coil of wire at the center of which 



a small magnet is suspended as shown 

 in Fig. 17. The suspended magnet 

 carries a pointer which plays over a 

 divided circle by means of which one 

 may observe the angle $ through 

 which the suspended magnet is turned 

 when a current 7 is sent through 

 the coil. The coil is mounted with 

 its plane vertical and magnetic north 

 and south as may be seen from Fig. 

 18. 



When no current is flowing 

 through the coil the suspended 



magnet ns points in the direction of H' (the horizontal com- 

 ponent of the earth's magnetic field). When a current of / 



sect ion of coil 

 (9 turns) 



'to battery 



Fig. 17. 



Circular coil of two turns 

 with small magnet suspended 

 at its center. 



suspended 



section of coil 



Fig. 18. 

 The plane of the paper is a horizontal plane. 



abamperes flows through the coil the field h f = - according 

 to Art. 14) is produced, and the suspended magnet points in the 



* See statement concerning the tangent galvanometer in Art. 12. 



