A 4V battery is connected across A and B as shown. The resistance of the diode is Zero in forward bias and infinity in reverse bias. The current supplied by the battery in the circuit is
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Zero
A p-n junction diode conducts only when its p-side (the arrow side) is connected to the higher potential. Otherwise it is reverse biased and, as stated in the question, its resistance is infinite.
Reading the figure: in the cell symbol the longer line is the positive terminal, which is B. Conventional current therefore leaves the cell at B, passes through the 40 Ω resistor and reaches the diode at its bar (n-side) end, that is, against the arrow.
The diode is reverse biased, so \( R_{\mathrm{diode}} \to \infty \).
\( \displaystyle I = \frac{4\,\mathrm{V}}{R_{\mathrm{diode}}+40\,\Omega} \to 0 \)