120 ADVANCED ELECTRICITY AND MAGNETISM. 



Note. In this problem treat the ship as one long slim iron bar parallel to the 

 keel. The field T f is equal to kH sin so that the value of the factor k can 

 be found from Fig. pqa, a being the known compass error and H being taken 

 as unity. The value of T" is kH sin <f>, so that the compass error /3 can be 

 calculated from Fig. P4b. 



Xi x J 



x> 4?o 



Fig. 



Fig. 



5. A ship's head is due magnetic north and P' the perpen- 

 dicular-to-the-deck component of the field at the compass due 

 to the ship's permanent magnetism is downwards and equal to 

 0.05 gauss. Find the deflection of the compass due to heeling 

 when the ship heels over 20 to the west, the horizontal component 

 of the earth's field at the compass being 0.16 gauss. Ans. 6 6' 

 to the east. 



6. Find the deflection of the compass due to heeling when the 

 ship heads magnetic northeast and heels 20 to the southeast, 

 other data being as in the previous problem. Ans. 4 to the west. 



