A body charged with electricity causes or “induces” charges on neighboring bodies. The process in this case is called electrostatic induction.
A magnet induces magnetism in neighboring masses of iron or other magnetic materials by the process of magnetic induction.
Again, a moving magnet induces electric currents in neighboring conductors by the process of electromagnetic induction.
Faraday’s Discovery.—All dynamos of whatever form, are based upon the discovery made by Faraday[11] in 1831, which may be stated as follows:
Electric currents are generated in conductors by moving them in a magnetic field, so as to cut magnetic lines of force.
Ques. What does the expression “cut lines of force” mean?
Ans. A conductor, forming part of an electric circuit, cuts lines of force when it moves across a magnetic field in such manner as to alter the number of magnetic lines of force which are embraced by the circuit.
It is important to clearly understand the meaning of this expression, which will be later explained in more detail.
Faraday’s Machine.—After various experiments, Faraday made his “new electrical machine” as shown in fig. 126. This piece of apparatus is preserved and was shown in perfect action by Prof. S. P. Thompson in a lecture delivered April 11th, 1891, after an interval of sixty years.