The resistance of a reverse biased $P-N$ junction diode is about

Ohm's law fails in

Consider a circuit consisting of a capacitor $(20 \mu\text{F})$, a resistor $(100 \Omega)$, and two identical diodes as shown in the figure. The resistance of each diode under forward biasing condition is $10 \Omega$. The time constant of the circuit is $\alpha \times 10^{-3} \text{ s}$. The value of $\alpha$ is . . . . . . .

Which of the following circuits represents a forward biased diode? Choose the correct answer from the options given below.

Can we take one slab of $p-$type semiconductor and physically join it to another $n-$type semiconductor to get $p-n$ junction?

In the given circuit,the voltage across the $P-N$ junction diode remains constant at $0.5 \ V$ regardless of the current. The maximum power rating of the diode is $100 \ mW$. What should be the value of $R$ in $\Omega$ to obtain the maximum current in the circuit?