A bridge circuit is a special type of electrical circuit wherein the current from a voltage source splits into two parallel paths. These parallel paths contain components (such as resistors, capacitors, and inductors), the types and arrangement of which depend on what the purpose of the bridge circuit is.  The parallel paths recombine again to let the current return to the source in a single conductor, thereby closing the circuit. 

The parallel paths are 'bridged' together by another electrical path that usually contains a load or a measuring device (such as a galvanometer), hence the name 'bridge circuit.'  Bridge circuits are primarily used in measurement applications and power supplies.

The best known bridge circuit is the Wheatstone Bridge, which is shown in Figure 1. Here, one can see that the circuit splits into two paths; the left path contains R2 and R1 while the right path contains R3 and Runknown.  The two parallel paths are bridged together by an ammeter or galvanometer connected between nodes A and B. 

The Wheatstone Bridge is used for accurately measuring the value of Runknown, provided that the values of the other resistors are known and may be adjusted.  To know more about how a Wheatstone Bridge works, please see this separate article on the Wheatstone Bridge.

Figure 1.  The Wheatstone Bridge

Aside from the Wheatstone Bridge, there are many other bridge circuits, the more widely known of which are as follows:

1)  Wien Bridge

2)  Schering Bridge

3)  Hay Bridge

4)  Owen Bridge

5)  Maxwell Bridge

6)  Resonance Bridge

See Also:   More Articles