Meter Bridge or Slide Wire Bridge :
This is the simplest form of Wheatstone bridge and is especially useful for comparing resistances more accurately. The construction of the metre bridge is shown in the figure. It consists of one metre resistance wire clamped between two metallic strips bent at right angles and it has two points for connection. There are two gaps; in one of them an unknown resistance whose value is to be determined is connected and in another gap resistance box (known resistance) is connected
The galvanometer is connected with the help of jockey and the cell is connected across AC. After making connections, the jockey is moved along the wire and the null point is obtained. The segment of length `l` and `(1 00 -l)` form two resistances of the Wheatstone bridge, the other two resistances being `R` (known) and `S` (unknown). The wire used is of uniform material and cross-section. The resistance can be found with the help of the following relation:
`R/S=P/Q=(sigmal)/(sigma(100-l))=> R/S =l/((100-l))=>S=(R(100-l))/l`
Where `s` is the resistance per unit length of the wire and `l` is the length of the wire from one end where null point is obtained. The bridge is most sensitive when null point is somewhere near the middle point of the wire.
The galvanometer is connected with the help of jockey and the cell is connected across AC. After making connections, the jockey is moved along the wire and the null point is obtained. The segment of length `l` and `(1 00 -l)` form two resistances of the Wheatstone bridge, the other two resistances being `R` (known) and `S` (unknown). The wire used is of uniform material and cross-section. The resistance can be found with the help of the following relation:
`R/S=P/Q=(sigmal)/(sigma(100-l))=> R/S =l/((100-l))=>S=(R(100-l))/l`
Where `s` is the resistance per unit length of the wire and `l` is the length of the wire from one end where null point is obtained. The bridge is most sensitive when null point is somewhere near the middle point of the wire.