_Constancy of the resistance_.--A noticeable point in my cells is the
remarkable constancy of the resistance in sunlight. Allowing for
differences in the temperature, the currents, and the light, at different
times, the resistance of a cell in sunlight will remain practically
constant during months of use and experiments, although during that time
the treatments received may have varied the resistance in dark hundreds
of thousands of ohms--sometimes carrying it up, and at others carrying it
down again, perhaps scores of times, until it is "matured," or reaches
the condition in which its resistance becomes constant.
As has already been stated, the sensitiveness of a cell to light is
increased by proper usage. This increased sensitiveness is shown, not by
a lowered resistance in light, but by an increased resistance in dark.
This change in the cells goes on, more or less rapidly, according as it
is retarded or favored by the treatment it receives, until a maximum is
reached, after which the resistance remains practically constant in both
light and dark, and the cell is then "matured," or finished. The
resistance in dark may now be 50 or even 100 times as high as when the
cell was first made, yet, whenever exposed to sunlight it promptly shows
the same resistance that it did in the beginning.
Pages:
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113