Wheastone Bridge

By balancing four resistors until a meter read zero, it measured an unknown electrical resistance very precisely.

Maker

Queen and Company

Dimensions

overall: 8 1/2 in x 24 in x 16 in; 21.59 cm x 60.96 cm x 40.64 cm

Museum

National Museum of American History

Credit line

from Princeton University, Department of Physics, thru Frank Shoemaker

The museum's own record (Smithsonian, National Museum of American History)

Also answering “What is the electricity doing?” see all

Leyden Jar BatteryFessenden electrolytic radio signal detectorGeneral Radio type 726-A vacuum tube voltmeterVoltmeter / Ammeter, E-1