In circuit A, both (p−n) junction diode act as forward biasing. Hence, current flows in circuit A. Total resistance R is given by ‌‌
1
R
=‌
1
4
+‌
1
4
or ‌‌
1
R
=‌
2
4
or ‌R=2Ω According to Ohm's law ‌V‌=IAR ‌ or ‌‌8‌=IA×2 ‌ or ‌‌IA‌=4A In circuit B, lower p-n-junction diode is reverse biased. Hence, no current will flow but upper diode is forward biased so current can flow through it V=IBR or 8=IB×4 or IB=2A