It would be possible to deduce these results from an abstract
consideration of the matter from the point of view of the principle of
conservation of energy. But we prefer to reserve this point until a
general notion of the action of dynamo-electric machines has been given.
The following principles or generalized statements follow as a matter of
the very simplest consequence from the foregoing considerations:
(a) To induce a current in a coil of wire by means of a magnet there
must be relative motion between coil and magnet.
(b) Approach of a magnet to a coil or of a coil to a magnet induces
currents in the opposite direction to that induced by recession.
(c) The stronger the magnet the stronger will be the induced currents in
the coils.
(d) The more rapid the motion the stronger will be the momentary
current induced in the coils (but the time it lasts will, of course, be
shorter).
(e) The greater the number of turns in the coil the stronger will be the
total current induced in it by the movement of the magnet.
These points are of vital importance in the action of dynamo electric
generators. It remains, however, yet to be shown how these transient and
momentary induction currents can be so directed and manipulated as to be
made to combine into a steady and continuous supply.
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