. Conduction of electricity through gases and radio-activity; a text-book with experiments . e needle respectively, and F isthe torsional couple for a deflection of unit angle, then for adeflection 6 the relation given is F6 = a(V2-V1)[V3-UVi + V2)], where a is a constant. It follows from this that if V3 be verylarge compared with both V1 and V2 then ^(V1 -\-V2) maybe neglected and Fd=a(V1-V2)V» QUADRANT ELECTROMETER *3 and therefore for a given difference of potential between thequadrants the deflection 6 will be proportional to the potentialof the needle. It is found however by observation t
. Conduction of electricity through gases and radio-activity; a text-book with experiments . e needle respectively, and F isthe torsional couple for a deflection of unit angle, then for adeflection 6 the relation given is F6 = a(V2-V1)[V3-UVi + V2)], where a is a constant. It follows from this that if V3 be verylarge compared with both V1 and V2 then ^(V1 -\-V2) maybe neglected and Fd=a(V1-V2)V» QUADRANT ELECTROMETER *3 and therefore for a given difference of potential between thequadrants the deflection 6 will be proportional to the potentialof the needle. It is found however by observation that inmost electrometers the deflection at first increases with increaseof potential on the needle until it reaches a maximum and thendecreases with further increase of potential. Recently G. has developed a theory in which he accounts for thismaximum value for 6 followed by a decrease by the presenceof the air-gap between the quadrants which causes the capacityof the needle to alter as it moves past this air-gap. He obtainsa modified equation, namely, {F + 2bV*)6 = a{V2-V1)Vz,. Fig. 8. 14 APPARATUS AND GENERAL METHODS where b is a constant, and assuming as before that Vz is largecompared with V1 and V2 which is a fact in the ordinarymethod of using the instrument. From either theory it fol-lows though, that for a given potential of the needle, thedeflection is proportional to the difference of potential betweenthe two pairs of quadrants. In most cases in actual practicethis is the important condition as a basis of measurement. ii. Dolazalek Type of Electrometer.—The type of elec-trometer devised a few years ago by Dolazalek is, in the opinionof the author, the most useful and satisfactory instrument ofits kind made at the present time for the class of work withwhich we have to deal, and if an electrometer is to be acquiredfor a laboratory this type is most strongly recommended. Theadvantages of this instrument over older forms consist chieflyin the simplicity of co
Size: 1344px × 1860px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookid, booksubjectradioactivity
