Grinnell College Physics Museum

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Wheatstone Bridge

Cat. No. 4725

Post Office Bridge with Meter

This is a Wheatstone bridge designed to locate a short circuit in a telephone or telegraph line by measuring the resistance of the wire to the short. It is called a "post office bridge" because this design was adopted by the British Post Office, which operated telegraph and telephone services as well as delivered mail. This bridge, which is in a box, has a built-in galvanometer. The upper plugs determine a ratio and the lower rows are a standard resistance.

Double Bridge

Serial No.. 169623

Post Office Bridge

This is a Wheatstone bridge designed to locate a short circuit in a telephone or telegraph line by measuring the resistance to the short. It gets the name "post office bridge" from its adoption by the British Post Office, which operated telegraph and telephone systems in addition to delivering mail. The upper row of plugs determine a ratio and the lower rows are a standard resistance.

Decade Bridge

This decade bridge is a form of Wheatstone bridge, a device to measure electrical resistance. This bridge provides two of the four arms of the complete Wheatstone circuit, and the unknown and a standard resistor had to be added. A battery and galvanometer were also attached externally.