Dynamo, Shunt.
A dynamo whose field is wound in shunt with the external circuit. Two
leads are taken from the brushes; one goes around the field magnets to
excite them; the other is the external circuit.
In such a dynamo the lowering of resistance on the outer circuit takes
current from the field and lowers the electro-motive force of the
machine. Short circuiting has no heating effect.
Fig. 141. SHUNT DYNAMO.
Dynamo, Single Coil.
A dynamo whose field magnet is excited by a single coil. Several such
have been constructed, with different shapes of field magnet cores, in
order to obtain a proper distribution of poles.
Dynamo, Tuning Fork.
A dynamo in which the inductive or armature coils were carried at the
ends of the prongs of a gigantic tuning fork, and were there maintained
in vibration opposite the field magnets. It was invented by T. A.
Edison, but never was used.
Dynamo, Uni-polar.
A dynamo in which the rotation of a conductor effects a continuous
increase in the number of lines cut, by the device of arranging one part
of the conductor to slide on or around the magnet. (S. P. Thomson.)
Faraday's disc is the earliest machine of this type.