Improvements in Electrical Resistances.
Year: 1896

page_text: Date of Application, 17th, Sept., 1896
Complete Specification Left, 19th July, 1897--Accepted, 21st Aug., 1897
ONAL
Improvements in Electrical Resistances.
I, WILLIAM MORRIS MORDEY, of Redholm, Loughborough, in the County of
Leicester, Electrician, do hereby declare the nature of this invention to be as
follows:-
This invention has for its object the construction of high electrical resistances.
For this purpose carbon resistances have been used, consisting of a narrow line
of plumbago usually on a piece of ebonite, but such resistances, although cheap and
convenient, are very apt to alter in value and cannot be used with a higher E.M.F.
than a few volts per megohm. To overcome this defect and to enable cheap and
reliable resistances to be constructed especially suitable for ineasurement purposes
where high E.M.F.'s are to be used, and also suitable for use under ordinary
condition, I use very long and rather wide surfaces of some good and preferably
pliable insulator such as shellaced, paraffined or varnished paper, silk, parchment
or linen, which is coated on one or both surfaces with plumbago and mounted in any
convenient way so as to allow sufficient exposure for cooling purposes.
Dated this 17th day of Santamban 1906
Improvements in Electrical Resistances.
I, WILLIAM MORRIS MORDEY, of Redholm, Loughborough, in the County of
Leicester, Electrician, do hereby declare the uaturo of this invention and in what
manner the same is to be performed to be particularly described and ascertained in
and by the following statement :-
This invention has for its object the construction of high electrical resistances.
For this purpose carbon resistances have been usod, consisting of a narrow line
of plumbago usually on a piece of ebonite, but such resistances, although cheap and
convenient, are very apt to alter in value and cannot be used with a higher E.M.F.
than a few volts per meghom. To overcome this defect and to enable cheap and
reliable resistances to be constructed especially suitable for measurement purposes
where high E.M.F.'s are to be used, and also suitable for use under ordinary
conditions, I use very long and rather wide surfaces of some good and preferably
ID 1

page_text: pliable insulator such as ribbon or bands of ebonite or celluloid, or shellaced,
paraffined or varnished paper, silk, parchment or linen which is coated on one or
both surfaces with plumbago and mounted in any convenient way so as to allow
sufficient exposure for cooling purposes..
One convenient way of carrying out this invention, especially applicable in the
case of high resistances, such as one or more megohuis, is to use a long narrow strip
of a suitable insulator such as mentioned above, coated on one or both sides with a
thin film of plumbago, and rolled into a spiral.the-turns or convolutions of which
are separated by a light ebonite frame so as to admit of sufficient ventilation for
cooling purposes, the spiral resistanco so mounted being enclosed in a box and
provided with terminals connected to its ends.
Instead of plumbago I may use other conductors capable of being applied to an
insulator in the form of a very thin film, but for practical purposes plumbago answers
all requirements.
For a resistance of one megohm, a suitable conductor is a plumbago coated strip
of insulating material from 5 to 10 feet long with a conducting film about 1 inch wide.
The thickness and width of the conducting film determines the length of the strip
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what I
claim is :-
The construction and use of clectrical resistances substantially as herein before
described.