Two sources of equal emf are connected to an external resistance R. The internal resistance of the two sources are` R_(1) and R_(2) (R_(1) gt R_(1))`. If the potential difference across the source having internal resistance `R_(2)` is zero, then

Options

A. `R=R_(2)-R_(1)`
B. `R=R_(2) xx(R_(1)+R_(2))//(R_(2)-R_(1))`
C. `R=R_(1)R_(2)//(R_(2)-R_(1))`
D. `R=R_(1)R_(2)//(R_(1)-R_(2))`