Hay bridge is used mainly for the measurement of inductance. The Hay bridge is a type of alternating current (AC) bridge circuit that is used to measure the inductance of a coil. It consists of four resistors, two capacitors, and the coil to be measured. The bridge is balanced by adjusting the resistors and capacitors until the voltage across the coil is zero. The inductance of the coil can then be calculated from the values of the resistors and capacitors.
The Hay bridge is a more accurate method of measuring inductance than some other methods, such as the Maxwell bridge or the Owen bridge. This is because the Hay bridge is less sensitive to the effects of stray capacitance and inductance. The Hay bridge is also able to measure a wider range of inductance values than other bridges.