# Wheatstone bridge method for measurement of medium resistance

**Wheatstone bridge- **Balanced Bridge condition

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

I_{1}=I_{3} and I_{2}=I_{4}

V_{bc}=V_{de} and V_{ab}=V_{ad}

V_{bc}=I_{3}R_{3}

V_{dc}=I_{4}R_{4}

As V_{bc}=V_{dc}

I_{3}R_{3}=I_{4}R_{4}

I_{3}/I_{4}=R_{4}/R_{3}

V_{ab}=I_{1}R_{1} and V_{ad}= I_{2}R_{2}

As V_{ab}=V_{ad}

I_{1}R_{1}=I_{2}R_{2}

I_{1}/R_{2}=I_{2}/R_{1}

As I_{3}=I_{1} and I_{2}=I_{4}

I_{3}/I_{4}=I_{1}/I_{2}

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

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

**R _{3}=R_{4}×R_{1}/R_{2} (Proved)**

** ****Advantages-**

- It can measure the medium range resistance (1 Ω <R<1 kΩ).
- The design is comparatively simpler compared to another bridge circuit.
- Calculation and complexity are less.

**Disadvantages-**

- Resistance value below 1Ω can’t be measured with this circuit.
- During the calculation of low resistance with the help of Wheatstone bridge, we can observe most of the voltage drop across the wire connections and the joint points by which the wire resistance becomes higher than the circuit resistance and it produce error while we measure low resistance value.

Also Read- Measurement of resistance

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