Explanation

(d) [image:3_image188.emf]
This is a series connection. Further, whatever current enters $A$ has to pass $.$ $I = 2\ A$.
The total resistance $= 6 + 9 + 5 = 20\Omega.$ The effective potential across the resistances is $20\Omega \times 2A = 40V.$ But $( + 12 - 4)V$ is opposing the potential difference caross $AB$ therefore the potential difference applied across $AB$ is $40V + 8V = 48V$