Dimmer.
An adjustable choking coil used for regulating the intensity of electric
incandescent lights. Some operate by the introduction and withdrawal of
an iron core as described for the choking coil (see Coil, Choking),
others by a damper of copper, often a copper ring surrounding the coil
and which by moving on or off the coil changes the potential of the
secondary circuit.
Dip of Magnetic Needle.
The inclination of the magnetic needle. (See Elements, Magnetic.)
Dipping.
(a) Acid or other cleaning processes applied by dipping metals in
cleaning or pickling solutions before plating in the electroplater's
bath.
(b) Plating by dipping applies to electroplating without a battery by
simple immersion. Copper is deposited on iron from a solution of copper
sulphate in this way.
Synonym--Simple Immersion.
Dipping Needle.
A magnet mounted in horizontal bearings at its centre of gravity. Placed
in the magnetic meridian it takes the direction of the magnetic lines of
force of the earth at that point. It is acted on by the vertical
component of the earth's magnetism, as it has no freedom of horizontal
movement. (See Magnetic Elements, and Compass, Inclination.)
Directing Magnet.
In a reflecting galvanometer the magnet used for controlling the
magnetic needle by establishing a field. It is mounted on the spindle of
the instrument above the coil and needle.
Synonym--Controlling Magnet.