P-N Junction Diode question from JEE Main 2022 (25 Jul, Shift 2)

Answer: 25

1. A is positive and B is negative.
2. The left diode (anode at A's junction) is forward biased: it acts as a short, so the left junction and the top node are the same point.
3. The right diode (anode at B's junction) is reverse biased: it acts as an open circuit.
4. Now the two $20\ \Omega$ resistors both join the A-node to the bottom node: $20 \parallel 20 = 10\ \Omega$.
5. This is in series with $15\ \Omega$: $R_{AB} = 10 + 15 = 25\ \Omega$.