Wheatstone Bridge

Wheatstone bridge is a type of electric circuit used to determine an unknown resistance (see Electric Circuit). It consists of four resistors whose arrangement is usually represented by the figure of a diamond.

Two of the circuit's resistors have known resistances. They come together at an angle and form the top half of the diamond. In the lower half, a resistor representing an unknown resistance is connected to a variable resistor that can be adjusted to a known resistance. A device called a galvanometer, which measures current, is connected to the top and bottom corners of the diamond to bridge the two halves of the circuit. The other corners are connected to a battery, which produces a current through the resistors. The variable resistor is adjusted until the voltage at the top and bottom corners of the circuit are equal. At this point, the galvanometer shows no current flow, and the circuit is said to be balanced.

Contributor: Robert B. Prigo, Ph.D., Prof. of Physics, Middlebury College.

Wheatstone Bridge

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