Two cells A and B of e.m.f 1.3 V and 1.5 V resp are arranged as shown in the figure. The voltmeter reads 1.45 V. The voltmeter is assumed to be ideal. Then show that r 1 = 3 r2 .

Let I be current in circuit and E₁=1.3V and E₂=1.5V  and E = 1.45V

by kirchoffs laws

(E₂-E₁)-I(R₁+R₂) = 0

and E = E₂ - IR₂

so , 0.05 = IR₂              .........(1)

      0.20=I(R₁+R₂)        .........(2)

on solvine above 2 eqns, we have R₁ = 3R₂ 

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regards

Ramesh