396
17.
SMALL CURRENT TECHNIQUE
Âlphcz Particle ÂctiviU.—From other studies it is known that
'
each alpha particle produces a total of approximately 1.74 X 105
ions.
Hence, if all the energy of the alpha particles was utilized in
the ionization process,
their number is equal to n/1.74 >< 105. In
the example above, 37 effective alpha particles were emitted each
second, or 37 atoms disintegrated in unit time. From the denition
given in 'section 11—3, the activity
was 10*6 millicuries.
Thus,
%= n/(1.74 X 105) (3.71 >< 107) millicuries. This is the activity
observed by the electroscope. Other atoms may have disinte—
grated: atoms whose alpha particles were absorbed in the radioactive
material.
A comparison of the activities of a known and unknown
material requires their use in approximately equal areas and thick—
nesses and that they be placed in the same position in the electroscope.
Usually, very thin layers of the active substance are
'
,
used.
'
.
'
ELECTROME'Ï‘ERS
—
17—8.
Principle and Use of the Quadrant Electrometer.—This
instrument is used to measure currents and voltages. It operates
on the principle of electrostatic repulsion. Essentially, there are
three parts: two xed conductors, called the quadrants, and a suspended conductor, called the needle.
As ordinarin used, the
needle is charged to a high xed potential (100 volts) and a differ_
ence of potential is applied between the quadrants. The needle is
_attracted toward one of the quadrants and repelled by the other.
The rate at which the needle moves is ameasure of the current and
»
the nal deeetion is a measure of the difference of potential be_
_
"twee*theqùadrants.
_
.
_
-
_
quadrant electrometer is generally used to measure cur—
rents
from about 10_“8 ampere (the usual limit of the
a;5ÏïÿÎç-eï5ÔïiîàrÿïWal‘1;typegalvanomeœr) to 10Î15"0r 10_—16 of an ampere
(SUChaSPTOdUCCCÏIHagaSby the action of radi0active substances,
X““Y$ŒUÏfra-VIOIetllght) It
be ad ap
for measurementSOf
V1tsandmtheSpeœalKelvmform1t Win
_
measure manythw
17.
SMALL CURRENT TECHNIQUE
Âlphcz Particle ÂctiviU.—From other studies it is known that
'
each alpha particle produces a total of approximately 1.74 X 105
ions.
Hence, if all the energy of the alpha particles was utilized in
the ionization process,
their number is equal to n/1.74 >< 105. In
the example above, 37 effective alpha particles were emitted each
second, or 37 atoms disintegrated in unit time. From the denition
given in 'section 11—3, the activity
was 10*6 millicuries.
Thus,
%= n/(1.74 X 105) (3.71 >< 107) millicuries. This is the activity
observed by the electroscope. Other atoms may have disinte—
grated: atoms whose alpha particles were absorbed in the radioactive
material.
A comparison of the activities of a known and unknown
material requires their use in approximately equal areas and thick—
nesses and that they be placed in the same position in the electroscope.
Usually, very thin layers of the active substance are
'
,
used.
'
.
'
ELECTROME'Ï‘ERS
—
17—8.
Principle and Use of the Quadrant Electrometer.—This
instrument is used to measure currents and voltages. It operates
on the principle of electrostatic repulsion. Essentially, there are
three parts: two xed conductors, called the quadrants, and a suspended conductor, called the needle.
As ordinarin used, the
needle is charged to a high xed potential (100 volts) and a differ_
ence of potential is applied between the quadrants. The needle is
_attracted toward one of the quadrants and repelled by the other.
The rate at which the needle moves is ameasure of the current and
»
the nal deeetion is a measure of the difference of potential be_
_
"twee*theqùadrants.
_
.
_
-
_
quadrant electrometer is generally used to measure cur—
rents
from about 10_“8 ampere (the usual limit of the
a;5ÏïÿÎç-eï5ÔïiîàrÿïWal‘1;typegalvanomeœr) to 10Î15"0r 10_—16 of an ampere
(SUChaSPTOdUCCCÏIHagaSby the action of radi0active substances,
X““Y$ŒUÏfra-VIOIetllght) It
be ad ap
for measurementSOf
V1tsandmtheSpeœalKelvmform1t Win
_
measure manythw