In explaining to you the construction and working of dynamo-machines,
we did not state anything about the amounts of wire used in winding the
machine.
It is not our intention to say exactly how much is used on any one
dynamo, because that is among the things you will have to learn when
you come to study the subject of electricity more deeply.
We simply want to have you understand that upon the number of turns of
wire on any one machine depends the effect that that amount of wire,
carrying electricity, will have upon a certain weight of iron when the
armature is revolved a certain number of turns per minute.
A certain number of strands of wire on an armature will only do a
certain amount of work at the most, so you will see that a small dynamo
will not produce as much electricity as a larger one containing more
iron and wire. For high pressure there must be more strands of wire
cutting the lines of force more frequently than would be required for
low pressure; and, to produce a great many ampères, the armature must
be larger and the wire upon it thicker than it would need to be if only
a small number of ampères were wanted.
This of itself is a very deep and complicated subject, and many books
have been written upon it alone. We shall, therefore, not attempt to go
more deeply into it in this little book, but simply content ourselves
with giving you the general idea, which will be sufficient until you
make a thorough study of the subject.