Unidirectional. adj.
Having one direction as a "unidirectional current" or "unidirectional
leak." The term is descriptive, and applicable to many cases.
Uniform. adj.
Unvarying; as a uniform potential difference, uniform current or
conductor of uniform resistance per unit of length. The term is
descriptive, and its application and meaning are obvious.
Uniform Field of Force.
A field of evenly distributed force; one in which the number of lines of
force per unit of area of any equipotential surface is the same.
Unipolar. adj.
Strictly speaking this term means having only one pole, and is applied
to magnets, armatures and the like. In its use a solecism is involved,
for there is no such condition possible as unipolar magnetism or
distribution of magnetism. An example of its use is shown in unipolar
magnets. (See Magnet, Unipolar.)
Unipolar Armature.
An armature of a unipolar dynamo; an armature whose windings
continuously cut the lines of force about the one pole, and hence whose
polarity is unchanged in its rotation.
Unipolar Current Induction.
Current induction produced by moving a conductor through a magnetic
field of force so that it always cuts the lines in similar relation to
itself. Thus it produces a constant current through its own circuit, if
a closed one, and no commutator is required. As this case always in
practice amounts to the cutting of lines of force in the neighborhood of
a single pole the term unipolar is employed to designate the action.
The simplest representation of unipolar induction is the rotating of a
conductor around the end of a bar magnet, its axis of rotation
corresponding with the axis of the magnet.
Unipolar Dynamo.
A dynamo in which one part of the conductor slides on or around the
magnet, so as always to cut lines of force near the same pole of the
magnet.
Unit.
A directly or indirectly conventional and arbitrary quantity, in terms
of which measurements of things with dimensions expressible in the
chosen units are executed.
Thus for length the c. g. s. unit is the centimeter; the B. E. unit is
the foot.