Question: Q. 4. In an unbiased $p-n$ junction, holes diffuse from the $p$-region to $n$-region because
(a) free electrons in the $n$-region attract them.
(b) they move across the junction by the potential difference.
(c) hole concentration in $p$-region is more as compared to $n$-region.
(d) All the above.
[NCERT Exemplar]
Ans Correct option : (c)
Explanation : The diffusion of charge carriers across a junction takes place from the regions of higher concentration to lower concentration. In this case, the $p$-region has greater concentration of holes than the $n$-region. Hence, in an unbiased $p-n$ junction, holes diffuse from the $p$-region to the $n$-region.
Q. 5. When a forward bias is applied to a $p-n$ junction, it
(a) raises the potential barrier.
(b) reduces the majority carrier current to zero.
(c) lower the potential barrier.
(d) None of the above
[NCERT Exemplar]
Show Answer
Solution:
Ans. Correct option : (c)
Explanation: When a forward bias is applied to a $p-n$ junction, it lowers the value of potential barrier. In the case of a forward bias, the potential barrier opposes the applied voltage. Hence, the potential barrier across the junction gets reduced.
