NEET Physics Questions: Semiconductor Electronics: Materials, Devices and Simple Circuits

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C, Si and Ge have same no. of valence electrons. C is an insulator because energy required to take one electron out from




Carbon (C) is an insulator because the energy required to excite an electron from the valence band to the conduction band is much higher in carbon than in silicon (Si) or germanium (Ge). This means that fewer electrons are available for conduction in carbon compared to silicon and germanium.
Ionization energy of isolated phosphorous atonis 10 eV. Ionization energy of same atom in Si is nearly________- eV (Relative Permitivity of silicon = 12)




Out of 5 valence electrons of phosphorous, 4 are shared with Si. Fifth electron can be approximated to revolve around nucleus. Situation is like H-atom $ En \approx -13.6 /n^2 ev $ for n = 1 , EN = -13.6 ev $E inside lattice = { En \over \epsilon_1^2 } = { -13.6 \over 12^2} =0.1 ev $
By adding impurity in intrinsic semiconductor P type semiconductor is made. Charge of these P type semiconductor is




A P-type semiconductor is created by doping an intrinsic semiconductor with a trivalent impurity (such as boron). This leads to the creation of 'holes' which can accept electrons. However, the overall charge of the P-type semiconductor remains neutral because the number of positively charged holes is balanced by the number of negatively charged electrons.
Strong overlaping of different atomic orbitals makes




Strong overlapping of different atomic orbitals in a solid leads to the formation of energy bands. These energy bands are crucial in determining the electrical properties of materials, such as whether they behave as conductors, semiconductors, or insulators.
We can not make p-n junction diode by making P type semi-condutor join with N - type semi-conductor, because




No explanation available.
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For p-n junction, which statement is incorrect




No explanation available.
The intrinsic semi-conductor has :




An intrinsic semiconductor has a finite resistance that decreases with temperature. As temperature increases, more electron-hole pairs are generated, thereby increasing the number of charge carriers and decreasing the resistance.
The behaviour of Ge as semi-conductor is due to width of :




The behavior of germanium (Ge) as a semiconductor is due to the width of the forbidden band being small and narrow. In semiconductors, the forbidden band (also called the band gap) is small enough to allow electrons to jump from the valence band to the conduction band at room temperature, thus allowing the material to conduct electricity.
Which of the following is not the advantage of PN junction diode over tube valve ?




The advantage of a PN junction diode over a tube valve that is not true is 'Unlimited life'. While PN junction diodes do have many advantages such as no warming-up time, large efficiency, and low power consumption, they do not have an unlimited lifespan. They can degrade over time due to factors such as heat and electrical stress.
A current gain for a transistor working as CB amplifier is 0.90. If emitter current is 10 mA, then base current is




$ \alpha = { I_c \over I_e } $ $ \therefore I_c = \alpha I_E = 9mA $ $ I_B = I_E -I_C = 10-9 =1 mA $
For a transistor $ { I_c \over I_E } =0.96 $, then CE current gain is :




$ \beta = { \alpha \over 1 -\alpha } $
At 0 K temp, a N - type semi-conductor




At 0 K temperature, an N-type semiconductor does not have any charge carriers. At absolute zero, all the electrons in the semiconductor are bound to atoms and there is no thermal energy to excite electrons into the conduction band. Hence, there are no free charge carriers (electrons or holes) available for conduction.
In Si-crystal, impurity donor atom have valency.




In a silicon crystal, an impurity donor atom typically has a valency of 5. Such atoms are called pentavalent impurities and they donate extra electrons to the silicon crystal, making them n-type semiconductors. Examples of pentavalent impurities include phosphorus (P), arsenic (As), and antimony (Sb).
A N-P-N transistor conducts when collector is______ and emitter is_____ with respect to base.




No explanation available.
A full wave rectifier is operating at 50Hz, 220V the fundamental frequency of ripple will be




A full wave rectifier converts both halves of the AC input signal into pulsating DC. Therefore, the ripple frequency of a full wave rectifier is twice the frequency of the AC supply. Given the AC supply frequency is 50Hz, the ripple frequency will be 2 * 50Hz = 100Hz.