Multiple Wire Method for Working Electro-magnets.
A method for suppressing sparking in working electro-magnets
intermittently. The magnet core is wound with a number (from four to
twenty) of separate layers of fine wire. A separate wire is taken for
each layer and all are wound in the same direction, from one end to the
other of the space or bobbin without returning. The ends are then joined
so as to bring all the wires in parallel. The effect of this is that as
the coils vary in diameter the time constants of each is different from
that of the others, the coefficient of self-induction being less, and
the resistance being greater for the coils farthest from the central
axis. Thus the extra currents run differently in the different coils,
and only a comparatively small spark can be produced owing to the
division of forces thus brought about.
Fig. 249. DIAGRAM ILLUSTRATING MULTIPLE WIRE WORKING.
Multiplex Telegraphy.
Any system of telegraphy transmitting more than four messages
simultaneously over a single wire. Properly it should apply to all
transmitting more than one, but conventionally has the above restricted
meaning, distinguishing it from duplex and quadruplex telegraphy.
Multiplying Power of a Shunt.
When a resistance is placed in parallel with a galvanometer on a circuit
the following relation obtains. Let s and g equal the resistances of the
shunt and galvanometer respectively, S and G the currents in amperes
passing through them, V the potential difference between their common
terminals, and A the whole current in amperes. Then we have
A = ( (s + g ) / s ) * G
and ( (s + g ) / s ) is termed the multiplying power of the shunt, as it
is the factor by which the current passing through the galvanometer must
be multiplied by to produce the total current.
Muscular Pile.
A species of voltaic battery, often termed Matteueci's pile, made up of
alternate pieces of muscle cut longitudinally and transversely
respectively. The different pieces represent the elements of a battery,
and their difference of potential is naturally possessed by the pieces.
Myria.
A prefix; one million times. Thus myriavolt means one million volts.
[Transcriber's note: Contemporary usage is mega, as in megavolt.]