Guard Ring.
An annular horizontal surface surrounding the balanced disc in the
absolute electrometer. (See Electrometer, Absolute.)
Guard Tube.
A metal tube surrounding a dry pile used with a quadrant electrometer,
or other electrometers of that type. It prevents the capacity of the
lower brass end of the pile (which brass end closes the glass tube
containing the discs) from momentary change by approach of some
conductor connected to the earth. There are other guard tubes also.
Gun, Electro-magnetic.
An electro-magnet with tubular core. If, when it is excited a piece of
an iron rod is pushed into the central aperture of the core and is
released, the magnetic circle will try to complete itself by pushing the
rod out so that it can thus be discharged, as if from a popgun.
Synonym--Electric Popgun.