# Maxwell bridge is used to measure

### Right Answer is:

Inductance

#### SOLUTION

**A Maxwell bridge is a modification to a Wheatstone bridge used to measure an unknown inductance** (usually of low Q value) in terms of calibrated resistance and inductance or resistance and capacitance.

As in the balanced condition of the Wheatstone bridge product of opposite arms, resistance is equal i.e

R_{1}R_{3} = R_{2}R_{4}

In Maxwell AC bridge in the two arms, there are two pure resistances so that for balance relations, the phase balance depends on the remaining two arms.

For the balanced condition of the Maxwell AC bridge

**Z _{1}Z_{3} = Z_{2}Z_{4}**

Where Z_{1} is the unknown Impedance

**Z _{1} = R_{1} + JX_{1} = R_{1} + JωL_{1}**

Z_{4} is the know Impedance

**Z _{4} = R_{4} + JX_{4} = R_{4} + JωL_{4}**

R_{2} and R_{3} = Known pure resistance

∴ **(R _{1} + JωL_{1})R_{3} = (R_{4} + JωL_{4})R_{2}**

Equating real and Imaginary part

**R _{1}R_{3} = R_{2}R_{4}**

&

**ωL _{1}R_{3} = ωL_{4}R_{2}**

**L**

_{1}R_{3}= L_{4}R_{2}Hence, the unknown self-inductance can be measured in terms of the known inductance L_{4} and the two resistors. Resistive and reactive terms balance independently and the conditions are independent of frequency. This bridge is often used for measuring the iron losses of the transformers at audio frequency.