good in one type of machine will not always answer in another, but the
general laws of electricity and magnetism must be observed in all cases.
With a given energy expressed in watts, we can arrange a quantity of
wire and iron to produce a certain quantity of work; the smaller the
quantity of material employed, and the larger the return for the energy
put in, the greater is the total efficiency of the machine.

Powerful electro-magnets, judiciously arranged, must make powerful
motors. The ease with which powerful electro-magnets can be constructed
has led many to believe that the power of an electro-motor can be
increased almost infinitely, without a corresponding increase of energy
spent. The strongest magnet can be produced with an exceedingly
small current, if we only wind sufficient wire upon an iron core. An
electro-magnet excited by a tiny battery of 10 volts, and, say,
one ampere of current, may be able to hold a tremendous weight in
suspension, although the energy consumed amounts to only 10 watts, or
less than 1/75 of a horse power, but the suspended weight produces no
mechanical work. Mechanical work would only be done if we discontinued
the flow of the current, in which case the said weight would drop; if
the distance is sufficiently small, the magnet could, by the application
of the current from the battery, raise the weight again, and if that
operation is repeated many times in a minute, then we could determine
the mechanical work performed. Assuming that the weight raised is 1,000
lb., and that we could make and break the current two hundred times
a minute, then the work done by the falling mass could, under no
circumstances, equal 1/75 of a horse-power, or 440 foot-pounds; that is,
1,000 lb. lifted 2.27 feet high in a minute, or about one-eighth of an
inch for each operation: hence the mere statical pull, or power of the
magnet, does in no way tend to increase the energy furnished by the
battery or generator, for the instant we wish to do work we must have