Leakage Conductor.
A conductor placed on telegraph poles to conduct directly to earth any
leakage from a wire and thus prevent any but a very small portion
finding its way into the other wires on the same pole. It presents a
choice of evils, as it increases the electrostatic capacity of the line,
and thus does harm as well as good. It consists simply of a wire
grounded and secured to the pole.
Leg of Circuit.
One lead or side of a complete metallic circuit.
Lenz's Law.
A law expressing the relations of direction of an inducing current or
field of force to the current induced by any disturbance in the
relations between such field and any closed conductor within its
influence. It may be variously expressed.
(a) If the relative position of two conductors, A and B, be changed, of
which A is traversed by a current, a current is induced in B in such a
direction that, by its electro-dynamic action on the current in A, it
would have imparted to the conductors a motion of the contrary kind to
that by which the inducing action was produced. (Ganot.)
(b) The new (induced) current will increase the already existing
resistances, or develop new resistance to that disturbance of the field
which is the cause of induction. (Daniell.)
(c) When a conductor is moving in a magnetic field a current is induced
in the conductor in such a direction as by its mechanical action to
oppose the motion. (Emtage.)
(d) The induced currents are such as to develop resistance to the change
brought about.
Letter Boxes, Electric.
Letter boxes with electrical connections to a bell or indicator of some
sort, which is caused to act by putting a letter into the box.
Leyden Jar.
A form of static condenser.
In its usual form it consists of a glass jar. Tinfoil is pasted around
the lower portions of its exterior and interior surfaces, covering from
one-quarter to three-quarters of the walls in ordinary examples. The
rest of the glass is preferably shellacked or painted over with
insulating varnish, q. v. The mouth is closed with a wooden or cork
stopper and through its centre a brass rod passes which by a short chain
or wire is in connection with the interior coating of the jar. The top
of the rod carries a brass knob or ball.
If such a jar is held by the tinfoil-covered surface in one hand and its
knob is held against the excited prime conductor of a static machine its
interior becomes charged; an equivalent quantity of the same electricity
is repelled through the person of the experimenter to the earth and when
removed from the conductor it will be found to hold a bound charge. If
the outer coating and knob are both touched or nearly touched by a
conductor a disruptive discharge through it takes place.