Honolulu star-bulletin. [volume] (Honolulu [Oahu, Hawaii]) 1912-2010, 1916-12-30

set up in the wire even if the cir
cult of which the wire forms part be
open. This induced pressure VIII ex-
list between the terminals of the cir
cult where it is opened just the same
as an electrical pressure exists be-
tween the terminals of battery that
is on an open circuit.
The question arises: Is the magnet
weakened when It is used in produc.
ing induced pressure in q wire, and, IL
not, what is the source of energy that
causes the current to exist in the
wire? The magnet is in no way weak
ened when it is used as described and
the induced current is produced by
the expenditure of muscular energy
In moving the. wire, just as the ex-
penditure of chemical energy in cell
produces an electrical current in a
closed electrical circuit in which the
cell is concealed.
When a wire with a current in it is
located in a magnetic field there is a
force acting on the wire which tends
to cause the wire to move across the
field. The direction of this force is
just the opposite to the one that must
be applied to the wire to cause it to
move, so there will be an induced pres
sure set up in the wire which will pro-
duee the current In other words, the
induced pressure set up in wire al
ways will be in such direction that
the current produced by it will OPP
pose the motion of the wire.
Current Induced by Moving Magnet
If a coil of wire be connected in
series of a galvanometer, as shown
in Figure 2, DETECTION of the gal
vanometer Indicator can be produced
by thrusting the magnet in and out
galvanometer indicator is DETECTED
when the magnet is moved inside the
coil is proof that there is current
produced in the circuit, and it must
be due to an induced pressure.
When the magnet is thrust into the
coil a DETECTION of the galvanometer
indicator will be produced, say, to the
right, and when the magnet is with
drawn the galvanometer indicator will
move to the left If the magnet be
turned end for end, the reflections of
the galvanometer indicator will be just
the reverse. If the coil itself be turned
end for end and the magnet placed in
its original position the DETECTION of
the galyanometer indicator produced
by movement of the magnet in or
out of the coil will correspond in d.
rection to those produced when the
coil was in it's original position and
the magnet had been turned end for
end.
Turns Of Wire
If the number of turns of wire COM
posing the coil be increased or de-
creased there will be corresponding
increase or decrease in the value OF
the induced pressure in the winding
of the coil due to given movement
of the coil and magnet with respect
to each other. The induced pressure
in the various turns of the coil will
act in the same direction, and the eff
fective pressure is equal to the sum
of the induced pressure in the various
turns The induced pressure in each
of the turns will have the same value
at dLg luSldulp pIONIuCu Gavin tuA IL ID
cutting the same number of lines of
force at that particular instant.
From the discussion above it is seen
that the induced pressure in an cleo
,trical circuit depends upon the follow
ing things:
(a) The velocity of the wire and
the magnetic field with respect TO
each other The greater the velocity
the greater the induced pressure, all
other things remaining constant.
(b) The strength of the magnetic
field-that is, the number of lines Of
force square centimeter. The
stronger the field the greater the in
duced pressure, all other things re-
naming constant
tc) The angle the path in which the
wire moves makes with the direction
of the magnetic field The nearer this
path is to being at right angles with
the direction of the magnetic field and
the axis of the wire the greater the
induced pressure.
Id The length of the wire actually
in the magnetic field The more wire