Question: Q. 7. In Figure, $V_{o}$ is the potential barrier across a $p-n$ junction, when no battery is connected across the junction
(a) 1 and 3 both correspond to forward bias of junction.
(b) 3 corresponds to forward bias of junction and 1 corresponds to reverse bias of junction.
(c) 1 corresponds to forward bias and 3 corresponds to reverse bias of junction.
(d) 3 and 1 both correspond to reverse bias of junction.
[NCERT Exemplar]
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Solution:
Ans. Correct option : (b)
Explanation: when $p-n$ junction is in forward bias, it compresses or decreases the depletion layer so potential barrier in forward bias decreases and in reverse layer so potential barrier in forward bias decrease and in reverse bias potential barrier increases.
Q. 8. Hole is
(a) an anti-particle of electron.
(b) a vacancy created when an electron leaves a covalent bond.
(c) absence of free electrons.
(d) an artificially created particle.
[NCERT Exemplar] Ans. Correct option : (b)
Explanation: Atoms of semiconductor are binding by covalent bonds between the atoms of same or different type. Due to thermal agitation when an electron leaves its position and become free, then it leaves a vacancy of electron, this vacancy in the bond (covalent) is called hole.
