The example for non-ohmic resistance is

What is the cause of the formation of the depletion layer in a $P-N$ junction?

For the circuit shown in the figure,$V_{AB} = $ ....... $V$.

The junction diode in the following circuit requires a minimum current of $1 \, mA$ to be above the knee point $(0.7 \, V)$ of its $I-V$ characteristic curve. The voltage across the diode is independent of current above the knee point. If $V_B = 5 \, V$,then the maximum value of $R$ so that the voltage is above the knee point will be:

In the given options,the diode that is forward biased is

Assuming the ideal diode,draw the output waveform for the circuit given in the figure. Explain the waveform.