If the magnet, N S, be now drawn away from the
circuit so that fewer of its lines of force passed through the circuit,
experiment shows the result that the current flowing in circuit will be
for the moment increased in strength, the _increase_ in strength being
proportional to the rate of _decrease_ in the number of lines of force.
So, on the other hand, if the magnet were pushed up toward the circuit,
the current in the circuit would be momentarily reduced in strength, the
decrease in strength in the current being proportional to the rate of
increase in the number of lines of force.
Similar considerations apply to the case of the simple circuit and the
magnet shown in Fig. 12. In this circuit there is no current flowing so
long as the magnet is at rest; but if the magnet be moved up toward
the circuit so as to _increase_ the number of lines of force that pass
through the circuit, there will be a momentary "inverse" current induced
in the circuit and it will flow in the _negative_ direction. While if
the magnet were moved away the _decrease_ in the number of lines of
force would result in a transient "direct" current, or one flowing in
the _positive_ direction.
Pages:
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92