Q.

A meter bridge with two resistances R1 and R2 as shown in the figure was balanced (null point) at 40 cm from the point P. The null point changed to 50 cm from the point P when 16Ω resistance is connected in parallel to R2. The values of resistances R1 and R2 are _______.            [2026]

1 R2=4Ω,  R1=43Ω  
2 R2=12Ω,  R1=123Ω  
3 R2=16Ω,  R1=163Ω  
4 R2=8Ω,  R1=163Ω  

Ans.

(4)

R1R2=4060=23    ...(1)

R1(R2×16R2+16)=5050R1=16R216+R2    ...(2)

23R2=16R216+R2

323+2R23=16

2R23=16-323=163

R2=8Ω

By equation (1)

R1=23R2=163Ω