Two cells of same emf are in series with an external resistance R. the internal resistance `r_1 gt r_2`. The p.d across the `1^(st)` cell found to be zero the value of R is

Options

A. `r_1 + r_2`
B. `r_1 - r_2`
C. `(r_1 + r_2)/2`
D. `(r_1 - r_2)/2`

Answer

B