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Question
Find the equivalent resistance of the network shown in figure between the points A and B.
(Assume that the resistance of each diode is zero in forward bias and is infinity in reverse bias.)
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Solution
Let the potentials at A and B be VA and VB, respectively.
(i) When VA > VB, that is, a battery is connected between points A and B, with its positive terminal connected to point A and its negative terminal connected to point B:
As the potential on the p-side of the diode is greater than the potential on the n-side of the diode, the diode is forward biased; thus, it can be replaced by a short circuit.
As the two resistances are connected in parallel, the effective resistance becomes
Equivalent resistance \[= \frac{10}{2} = 5 \Omega\]
(ii) When VA < VB:
The diode is reverse biased, so it is replaced by an open circuit. Thus, no current flows through this branch.
∴ Equivalent resistance = 10 Ω
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