Physics MCQs for NEET — Practice Questions with Answers

(a) Depletion layer consist of mainly stationary ions.

A PN junction diode is commonly used as a rectifier, which converts alternating current (AC) into direct current (DC). When forward-biased, the diode allows current flow in one direction, effectively rectifying the AC signal.

The depletion region or depletion layer is a region in a P-N junction diode where no mobile charge carriers are present. The depletion layer acts like a barrier that opposes the flow of electrons from the n-side and holes from the p-side. 

(c) After a large reverse voltage is PN-junction diode, a huge current flows in the reverse direction suddenly. This is called Breakdown of PN-junction diode.

(c) When polarity of the battery is reversed, the P-N junction becomes reverse biased so no current flows.

(d) Resistance in forward biasing ${\mathrm{R}}_{\mathrm{fr}}\approx 10\mathrm{\Omega }$ and resistance in reverse biasing ${\mathrm{R}}_{RW}\approx {10}^5\mathrm{\Omega }$

$\frac{{\mathrm{R}}_{\mathrm{fr}}}{{\mathrm{R}}_{\mathrm{RW}}}=\frac{1}{{10}^4}$

(d) The holes are created due to missing electrons.

(b) In forward biasing width of depletion layer decreases.

 During the formation of a junction diode, holes from p- region diffuse into n-region, and electrons from n-region diffuse into p-region. In both cases, when an electron meets a hole, they cancel the effect at each other and as a result, a thin layer at the junction becomes free from any of charges carriers. This is called the depletion layer. There is a potential gradient in the depletion layer, negative on the p-side, and positive on the n-side. The potential difference thus developed across the junction is called the potential barrier.