Q.

When two resistances R1 and R2 are connected in series and introduced into the left gap of a metre bridge and a resistance of 10Ω is introduced into the right gap, a null point is found at 60 cm from the left side. When R1 and R2 are connected in parallel and introduced into the left gap, a resistance of 3Ω is introduced into the right gap to get a null point at 40 cm from the left end. The product of R1R2 is ________ Ω2.                          [2023]


Ans.

(30)

R1+R210=6040=32  R1+R2=15

Now  R1R2(R1+R2)×3=4060=23  R1R2=30