North-seeking Pole.
The pole of a magnet which tends to point to the north; the north pole
of a magnet.
Null Method.
Any method of obtaining measurements or comparisons, in which the
measurement is correct when the deflection of the galvanometer or other
indicator is zero, nought or null. The Wheatstone Bridge (see Bridge,
Wheatstone) is an example of a null method.
Two obvious advantages attach to null methods in electric galvanometer
work. One is that an uncalibrated galvanometer can be employed. The
other is that a galvanometer of any high degree of sensitiveness can be
employed, there being no restriction as to its fineness of winding or
highness of resistance.
"Upper case Omega Graphic".
(Greek capital" Omega") symbol for megohm.
[Transcriber's note: Now used for ohms.]
"Lower case Omega Graphic".
(Greek omega) symbol for ohm.
[Transcriber's note: Now used for angular velocity, 2*PI*frequency.]
Occlusion.
An absorption of gases by metals. Palladium will, if used as the
hydrogen evolving electrode in decomposing water, absorb 980 times its
volume of hydrogen, which is said to be occluded. The metal may also be
heated in hydrogen and allowed to cool therein, when occlusion occurs.
Platinum will occlude 4 times its volume of hydrogen; iron, 4.15 times
its volume of carbon-monoxide; silver, 7 times its volume of oxygen.
Metals with occluded gases may serve as elements in a galvanic couple.
(See Gas Battery.) A metal expands in occluding a gas.
In the storage battery it is believed that occlusion plays a part,
hydrogen and oxygen being respectively absorbed by the two sets of
plates, and acting as they do in Groves' gas battery.
Oerstedt.
Name proposed for the unit of current strength, but not adopted. The
ampere is the accepted name.