|Object Name||Tester, Circuit|
Rotating drum, grooved and marked from 0 to 100 in 1-unit increments around circumference. Drum is turned with a protruding knob. Wood stand is marked "Fritz Kohler Leipzig."
The Wheatstone bridge, named for English scientist Charles Wheatstone in 1843, is an electrical circuit for comparing resistances. The term also applies to instruments, such as this one, that include those circuits. Popular in laboratories, the instruments came in many forms. The donor’s father, John Harper Long, bought this Wheatstone bridge while studying in Tübingen, Germany, in 1877. Long later became a professor of chemistry at Northwestern University Medical School in Chicago. He may have used this instrument to determine the electrical conductivity of blood, which he described in his 1905 textbook of physiological chemistry for medical students.
|Dimensions||H-5.5 W-6.375 D-6.25 inches|
|Credit line||American Philosophical Society|