Question

In the meterbridge experimental set up, shown in the figure, the null point ‘D’ is obtained at a distance of 40 cm from end A of the meterbridge wire. If a resistance of 10Ω is connected in series with R₁, null point is obtained at AD = 60 cm. Calculate the values of R₁ and R₂.

Answer 1

 Considering both the situations and writing them in the form of equations

Let R' be the resistance per unit length of the potential meter wire,

`R_1/R_2 = (R' xx 40)/(R'(100 -40) ) = 40/60 = 2/3`

`(R_1 + 10)/R_2 = (R' xx 60)/(R'(100 -60)) = 60/40 = 3/2`

`R_1/R_2 = 2/3 -------- (1)`

`(R_1 +10)/R_2 = 3/2   ---------(2)`

Putting the value of R1 from equation (1) and substituting in equation (2)

`2/3 + 10/R_2 = 3/2`

`R_2 = 12Ω`

Reca;;omg equation (1) again 

`R_1/12 = 2/3`

`R_1 = 8Ω`