Question

(a) State Kirchhoff's rules for an electric network. Using Kirchhoff's rules, obtain the balance condition in terms of the resistances of four arms of Wheatstone bridge.

(b) In the meter bridge experimental set up, shown in the figure, the null point 'D' is obtained at a distance of 40 cm from end A of the meter bridge wire. If a resistance of 10 ohm is connected in series with R₁, null point is obtained at AD = 60 cm. Calculate the values of R₁, and R₂.

Answer 1

(a) Junction rule : At any junction, the sum of the currents entering the junction is equal to the sum of currents leaving the junction.

Loop rule : The algebraic sum of the changes in potential around any closed loop involving resistors and cells is zero.

In loop ADBA

Substituting for R₂ and finding the value of R₁

                R₁  =  8 ohm