Chapter 14: Semiconductor Electronics Assertion Reason
These questions of two statements each, printed as Assertion and Reason. While answering these Questions you are required to choose any one of the following four responses.
(A) If both Assertion & Reason are true & the Reason is a correct explanation of the Assertion.
(B) If both Assertion and Reason are true but Reason is not a correct explanation of the Assertion.
(C) If Assertion is true but the Reason is false.
(D) If Assertion & Reason both are false.
Assertion-Reason Questions
- Assertion (A): Silicon is widely used in semiconductor devices.
Reason (R): Silicon has an energy band gap of about 1.1 eV which makes it a good semiconductor material.
Answer: Both A and R are true and R is the correct explanation of A. - Assertion (A): At absolute zero temperature, a semiconductor behaves like an insulator.
Reason (R): At absolute zero, all the electrons in a semiconductor are bound and there are no free electrons to conduct electricity.
Answer: Both A and R are true and R is the correct explanation of A. - Assertion (A): The resistance of a semiconductor decreases with an increase in temperature.
Reason (R): With an increase in temperature, more electrons get enough energy to jump from the valence band to the conduction band.
Answer: Both A and R are true and R is the correct explanation of A. - Assertion (A): The conductivity of an intrinsic semiconductor is increased by doping.
Reason (R): Doping introduces more charge carriers in the semiconductor, thereby increasing its conductivity.
Answer: Both A and R are true and R is the correct explanation of A. - Assertion (A): In a p-type semiconductor, holes are the majority charge carriers.
Reason (R): Doping a semiconductor with a trivalent impurity creates holes in the valence band.
Answer: Both A and R are true and R is the correct explanation of A. - Assertion (A): In an n-type semiconductor, electrons are the majority charge carriers.
Reason (R): Doping a semiconductor with a pentavalent impurity adds more free electrons to the conduction band.
Answer: Both A and R are true and R is the correct explanation of A. - Assertion (A): A p-n junction diode conducts current only when it is forward biased.
Reason (R): In forward bias, the potential barrier at the junction is reduced, allowing charge carriers to flow across the junction.
Answer: Both A and R are true and R is the correct explanation of A. - Assertion (A): The depletion region in a p-n junction is free of mobile charge carriers.
Reason (R): The depletion region is formed due to the diffusion of electrons and holes, leaving behind fixed ions.
Answer: Both A and R are true and R is the correct explanation of A. - Assertion (A): A zener diode is used for voltage regulation.
Reason (R): A zener diode maintains a constant voltage across it when operated in the breakdown region.
Answer: Both A and R are true and R is the correct explanation of A. - Assertion (A): The current through a p-n junction diode in reverse bias is very small.
Reason (R): In reverse bias, the potential barrier at the junction is increased, preventing the flow of majority carriers.
Answer: Both A and R are true and R is the correct explanation of A. - Assertion (A): The base of a transistor is made very thin and lightly doped.
Reason (R): This ensures that most of the charge carriers injected into the base from the emitter pass through to the collector.
Answer: Both A and R are true and R is the correct explanation of A. - Assertion (A): An n-p-n transistor is commonly used for amplification.
Reason (R): In an n-p-n transistor, electrons are the majority charge carriers which have higher mobility compared to holes.
Answer: Both A and R are true and R is the correct explanation of A. - Assertion (A): A photodiode is operated in reverse bias.
Reason (R): In reverse bias, the width of the depletion region increases, reducing the junction capacitance and making it more sensitive to light.
Answer: Both A and R are true and R is the correct explanation of A. - Assertion (A): LEDs emit light when forward biased.
Reason (R): In forward bias, electrons and holes recombine at the junction, releasing energy in the form of photons.
Answer: Both A and R are true and R is the correct explanation of A. - Assertion (A): The threshold voltage of a silicon diode is approximately 0.7 V.
Reason (R): The threshold voltage is the minimum forward voltage at which the diode starts to conduct significantly.
Answer: Both A and R are true and R is the correct explanation of A. - Assertion (A): The output characteristics of a transistor in the active region show that the collector current is almost independent of the collector-emitter voltage.
Reason (R): In the active region, the base-emitter junction is forward biased and the base-collector junction is reverse biased.
Answer: Both A and R are true and R is the correct explanation of A. - Assertion (A): The base current in a transistor is much smaller than the collector current.
Reason (R): The emitter current is the sum of the base and collector currents.
Answer: Both A and R are true and R is the correct explanation of A. - Assertion (A): A transistor can be used as a switch.
Reason (R): In the saturation region, the transistor acts as a closed switch, and in the cutoff region, it acts as an open switch.
Answer: Both A and R are true and R is the correct explanation of A. - Assertion (A): In a common-emitter transistor amplifier, the input signal is applied to the base-emitter junction.
Reason (R): The common-emitter configuration provides a phase shift of 180° between the input and output signals.
Answer: Both A and R are true and R is the correct explanation of A. - Assertion (A): The intrinsic carrier concentration in a semiconductor increases with temperature.
Reason (R): Higher temperatures provide more energy to electrons to jump from the valence band to the conduction band.
Answer: Both A and R are true and R is the correct explanation of A.