Meter Bridge | Principle | Formula

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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.




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





  • 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.






  • 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.




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-

Quiz on Meter Bridge


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Electric Cells & Batteries


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