**Wheatstone Bridge-**

Before you go through this article, make sure that you have gone through the previous article on **Wheatstone Bridge**.

**We have learnt-**

- A Wheatstone bridge is an arrangement of four resistances used to determine one of these resistances in terms of the remaining three resistances.
- It is a null method and is preferred over the other methods for determining the value of an unknown resistance.

**In this article, we will learn about Meter Bridge.**

**Meter Bridge-**

Meter bridge is the practical application of the Wheatstone bridge that is used to measure an unknown resistance. |

**Principle-**

**Its working is based on the principle of Wheatstone bridge. When the bridge is balanced, we have-**

**Construction-**

- It consists of a one meter long manganin wire of uniform cross-section.
- The wire is stretched along a meter scale fixed over a wooden board.
- The two ends of the wire are soldered to two L-shaped thick copper strips A and C.
- Between these two copper strips, another copper strip is fixed so as to provide two gaps.
- A resistance box is connected in one gap and the unknown resistance in the other gap.
- A source of emf E is connected across AC.
- A movable jockey and a galvanometer are connected across BD as shown in the figure.

**METER BRIDGE**

**Working-**

- A suitable resistance R is taken out from the resistance box.
- Then, the jockey is moved along the wire AC till there is no deflection in the galvanometer.
- This is the balanced condition of the Wheatstone bridge.

**If P and Q are the resistances of the parts AB and BC of the wire, then for the balanced condition of the Wheatstone bridge, we have-**

Let AB = ℓ cm, then BC = (100 – ℓ) cm.

**Since the wire is of uniform cross-section, therefore-**

**Resistance of wire ∝ Length of wire**

**where σ is the resistance per unit length of the wire.**

**Hence,**

**From here,**

**Knowing the values of ℓ and R, the value of unknown resistance S can be determined.**

**Determination of Resistivity-**

**If r is the radius of the wire and L is its length, then resistivity of its material is given by-**

**Test Your Concepts-**

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