Meter bridge:

 



1) Meter bridge is a system and application of Wheatstone bridge principle.



2) It contains a 1 meter length wire with uniform cross-sectional area.



3) A 100 cm or 1 meter scale is filled along the wire.



4) There is an another copper strip with two gaps, where two resistors can be put.



5) A known resistor of resistance R is put on the position X.



6) An unknown resistance S is put in the position Y.



7) A jockey is connected in between the two resistors with a galvanometer.



8) When the key is closed, the jockey is slided over the wire.



9) Now we get a position Z where the Jockey Galvanometer shows no deflection




10) That moment Wheatstone bridge is balanced and Wheatstone bridge principle is applied.




11) If r is the resistance per unit cm length of the wire. Then

AZ = l cm

ZB = 100 - l cm

Resistance of l cm = lr

Resistance of 100-l cm = (100-l) r




12) Now applying Wheatstone bridge principle we got

 



 

This is how we can calculate the resistance of an unknown resistor.