CHAP, x.] ELECTRICITY AND MAGNETISM. 357 



CHAPTER X. 



INDUCTION CURRENTS (Magneto-Electricity). 

 LESSON XXXVI. Currents produced by Induction. 



391. In 1831 Faraday discovered that currents can 

 be induced in a closed circuit by moving magnets near 

 it, or by moving the circuit across the magnetic field, 

 and he followed up this discovery by finding that a 

 current whose strength is changing may induce a 

 secondary current in a closed circuit near it, Such 

 currents, whether produced by magnets or by other 

 currents, are known as Induction Currents. And 

 the action of a magnet or current in producing such 

 induced currents is termed electromagnetic induc- 

 tion. 1 



392. Induction Currents produced by a Mag- 

 net. If a coil of insulated wire be connected in circuit 



.with a delicate (long- coil) galvanometer, and a magnet 

 be inserted rapidly into the hollow of the coil (as in Fig. 



1 The student must not confuse this electromagnetic induction with the 

 phenomenon of the electrostatic induction of one charge of electricity by 

 another charge, as explained in Lesson III., and which has nothing to do 

 with currents. Formerly, before the identity of the electricity derived from 

 different sources was understood (Art. 218), electricity derived thus from the 

 motion of magnets was termed magneto- electricity. For most purposes the 

 adjectives inagneto-electric and electro - magnetic are synonymous. The 

 production of electricity from magnetism, and of magnetism from electricity, 

 are, it is true, two distinct operations ; but both are included in the branch 

 of science denominated Electromagnetics. ^ 



