Like an Anderson Bridge, Hay Bridge is another modified version of Maxwell Wien Bridge. We mainly use this bridge when the phase angle of the measuring inductive impedance is large enough.

## Construction of Hay Bridge

The figure below is showing the general structure of a Hay Bridge. Here, across the arm AB there is a capacitor of capacitance C_{1} along with a very small resistance R_{1} in series with it. Now we connect the coil of unknown impedance in the opposite arm, that is arm CD. Besides that, we keep the remaining two arms BC and DA, entirely resistive with two known resistances R_{2} and R_{4}.

## Theory

We told earlier in this article that this bridge is a variation of Maxwell Wien Bridge. So, it is necessarily an AC Bridge. Hence, the balanced condition of a Hay bridge is the same as that of a general AC Bridge.

The bridge circuit is a general AC bridge shown just above. Let us write down the general balanced conditions of the AC Bridge.

Comparing with the general circuit of an AC Bridge we can write down the impedance of each arm of the above shown Hay Bridge as.

Hence, at the balanced condition,

Now, by equating the real and imaginary parts of the equation with zero we get,

From here we get,

- AC Bridges and Theory of AC Bridge
- Maxwell Bridge Construction and Theory of Maxwell Bridge
- Maxwell Wien Bridge Circuit and Theory
- Hay Bridge Circuit Construction and Theory of Hay Bridge
- Murray Loop Test for Finding Fault Location in Cable
- Anderson’s Bridge Circuit and Theory of Anderson Bridge
- Wheatstone Bridge Circuit Operation and Theory
- Schering Bridge Construction and Theory
- De Sauty Bridge Construction Circuit and Theory
- Heaviside Campbell Equal Ratio Bridge
- Owen Bridge Circuit and Theory of Owen Bridge
- Varley Loop Test for Finding Fault Location in Cable