Question

Two cells `a` and `B` of emf `1.3 V` amd `1.5V `respectively are arranged as shown in figure. The voltmeter reds `1.45V`. The voltmeter is assumed to be ideal. Then

A. `r_A = 2r_B`
B. `r_A = 3r_B`
C. `r_B= 2r_A`
D. `r_B = 3r_A`

Answer 1

Correct Answer - B
b. `1.45 = 1.3 + Ir_A`
`1.45 = 1.5 - Ir_B`
`Ir_B = 0.05`
`Ir_A = 0.15`
Dividing, we get `r_B/r_A = 1/3`
or `r_A = 3r_B` .