Question: Q. 10. (i) Explain with the help of a diagram the formation of depletion region and barrier potential in a $p-n$ junction.
(ii) Draw the circuit diagram of a half wave rectifier and explain its working.
U [Outside Delhi I, II, III 2016]
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Solution:
Ans. (i) Due to diffusion and drift, the electrons and holes move across the junctions, creating a final stage in which a region is created across the junction wall, which gets devoid of the mobile charge carriers. This region is called depletion region; the potential difference across the region is called Barrier potential. $1 / 2$
$\leftarrow \mathrm{E}$
(ii)
Working : If an alternating voltage is applied as input, a diode in series with a load, a pulsating voltage will appear across the load only during that half cycle of the ac input during which the diode is forward biased.
Therefore, in the positive half cycle of ac input there is current through the load resistor $R_{L}$ and we get an output voltage whereas there is no output during the negative half cycle. Thus, the output voltage is restricted to only one direction and is said to be rectified.
$1 \frac{1}{2}$
[Note : If the student draws only the input and output wave form, then award $1 / 2$ mark only]
[CBSE Marking Scheme 2016]
