ELECTROMOTIVE FORCE AND CURRENT. 3 



(from + to ). The relation between these three quantities 

 is most conveniently remembered by Fleming's rule, as 

 illustrated in the annexed Fig. 1. 



Direction 



of 



Induced 

 E.M.F. 



Direction 



of 

 Motion 



Right Hand. 

 FIG. l. FLEMING'S RULE FOR A GENERATOR. 



Using the right hand, and holding the thumb and first 

 two fingers so that each is perpendicular to the plane con- 

 taining the other two, the three directions are given as 

 follows : 



Thumb Direction of motion of conductor. 

 First finger Direction of lines of force. 

 Second finger Direction of electromotive force* 

 induced. 



The Magnetic Effects of a Current. A current flowing 

 in a straight conductor gives rise to a field composed 

 of circular lines of force, the plane of the circles being 

 perpendicular to the conductor, and their common centre 

 being the centre of the conductor. The direction of these 

 lines of force is related to the direction of the current in the 

 manner indicated in the following rule. 



Place the thumb of the right hand along the conductor so 

 as to point in the direction of flow of the current ; if the fingers 



* The following mnemonics may help the student in remembering 

 Fleming s rule : 



Thu -b Motion. 



.First finger Force. 



Se Gond finger Current, 



