MCQ
Two identical $p-ri$ junctions may be connected in series with a battery in three ways $($figure$)$. The potential difference across the two $p-n$. junctions are equal in:
  • A
    Circuit $1$ and circuit $2.$
  • Circuit $2$ and circuit $3$.
  • C
    Circuit $3$ and circuit $1.$
  • D
    Circuit $1$ only.

Answer

Correct option: B.
Circuit $2$ and circuit $3$.
In circuit $1$, one diode is forward biassed and the other diode is reverse biassed. The forward$-$biassed diode offers zero resistance $($ideally$)$ to the current flow, so it can be replaced by a short circuit. The voltage drop across the first diode will be zero. The second diode is reverse biassed, so it can be replaced by an open circuit; hence, the voltage drop across this diode will be maximum.
In circuit $2$, both the diodes are forward biassed, so they can be replaced by short circuits; hence, the voltage drop across both of them will be minimum and equal.
In circuit $3$, both the diodes are reverse biassed, so both can be replaced by open circuits; hence, the voltage drop across both of them will be maximum and equal.

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