Q. Two identical $p-n$ junctions are connected in series with a battery in three ways, as shown below The potential drops across the two $ p-n $ junctions are equal in

In This post you will get answer of Q.
Two identical $p-n$ junctions are connected in series with a battery in three ways, as shown below
The potential drops across the two $ p-n $ junctions are equal in

Solution:

The potential drops across the two p-n junction are equal in circuit 3 and circuit 1, because in circuit 2, N is connected with N which is not the condition of series combination of transistor.