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316 THE BOY ELECTRICIAN

They are bent at right angles and mounted on the base
on either side of the commutator with small round-headed
wood screws.

The. completed dynamo is shown in Figure 262. One

end of the shaft is pro-

 

 

 

 

 

go o vided with a small pulley

L— —— zi—Z— ——-*" to accommodate a small
F—"i’ -3 leather belt.

[1 o The dynamo is con-

0 nected as a “ shunt ” ma-

FIG. 26L_The Brushes. chine, that is, one terminal

of the field magnet is con-
nected to one of the brushes, and the other terminal to
the other brush.

A wire is then led from each of the brushes to a binding-
post.

A shunt dynamo will only generate when run in a certain
direction. In order to make it generate when run in the
opposite direction, it is necessary to reverse the field con-
nections.

The dynamo just described should have an output of
from IO to 15 watts and deliver about 6 volts and 1% to
2 I 2 amperes.

In order to secure current from the dynamo it will first
be necessary to magnetize the field by connecting it to sev-
eral batteries.

It will be found that the dynamo will also operate as a
very eflicient little motor, but that on account of having a

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