The equivalent resistance of the circuit across `AB` is given by
.

Options

A. `4 Omega`
B. `13 Omega`
C. `4 Omega` or `13 Omega`
D. `4 Omega` or zero

Answer

C

Explanation

If `V_(A) gt V_(B)` both the junction diodes are forward biased and the given circuit diagram becomes a balanced Wheatestone bridge The equivalent resistance in this case becomes `4 Omega`, if `V_(A) = V_(B)` the diodes are reverses biased in that case `4 Omega,5Omega` and `4 Omega` are in series.