ELECTRONICS-QUIZ 17

ELECTRONICS-QUIZ 17

Dear Readers,

As per analysis for previous years, it has been observed that students preparing for NEET find Physics out of all the sections to be complex to handle and the majority of them are not able to comprehend the reason behind it. This problem arises especially because these aspirants appearing for the examination are more inclined to have a keen interest in Biology due to their medical background. Furthermore, sections such as Physics are dominantly based on theories, laws, numerical in comparison to a section of Biology which is more of fact-based, life sciences, and includes substantial explanations. By using the table given below, you easily and directly access to the topics and respective links of MCQs. Moreover, to make learning smooth and efficient, all the questions come with their supportive solutions to make utilization of time even more productive. Students will be covered for all their studies as the topics are available from basics to even the most advanced. .

Q1. The emitter-base junction of a transistor is ………….. biased while the collector-base junction is ………….. biased.

•  Forward, forward
•  Forward, reverse
•  Reverse, forward
•  Reverse, reverse

Solution
(b) In a transistor amplifier for better amplification the emitter-base junction of a transistor is forward biased while the collector-base junction is reverse biased.

Q2.Name of a p-n junction, which can be used as the regulator, is

•  Zener diode
•  Tunnel diode
•  Gunn diode
•  None of these

Solution
(a) Zener diode has a relatively constant voltage across it, regardless of the value of current through the device. This permits the zener diode to be used as a voltage regulator.

Q3. In a triclinic crystal system

•  a≠b≠c,α≠β≠γ
•  a=b=c,α≠β≠γ
•  a≠b≠c,α≠β=γ
•  a=b≠c,α=β=γ

Solution
(a) In a triclinic crystal a≠b≠c and α≠β≠γ≠90°

Q4. The junction diode in the following circuit requires a minimum current of 1mA to be above the knee point (0.7 V) of its I-V characteristic curve. The voltage across the junction diode is independent of current above the knee point, if V_B \=4V,
then the maximum value of R so that the voltage is above knee point will be

•  3.3 kΩ
•  4.0 kΩ
•  4.7 kΩ
•  6.6 kΩ

Solution
(a) V_B=V_knee+IR or 4=0.7+10^-3 R or R=3.3/10^-3=3.3×10³ Ω

Q5.In the following circuit, a voltmeter V is connected across a lamp L. What change would occur in voltmeter reading

if the resistance R is reduced in value

•  Increases
•  Decreases
•  Remains same
•  None of these

Solution
(a) Here the emitter base junction of N-P-N transistor is forward biased with battery V_BBthrough resistance R. When the value of R is reduced, then the emitter current i_e will increase. As a result the collector current will also increase. (i_c=i_e-i_b). Due to increase in i_c, the potential difference across L increases and hence the reading of voltmeter will increases  

Q6. In extrinsic semiconductors

•  The conduction band and valence band overlap
•  The gap between conduction band and valence band is more than 16 eV
• The gap between conduction band and valence band is near about 1 eV
•  The gap between conduction band and valence band will be 100 eV and more

Solution
(c)the gap between conduction band and valence band is near about 1 eV

Q7.The density for a fcc lattice is (A=atomic wt., N=Avogadro’s number, a=lattice parameter)

•  4A/(Na³ )
•  2A/(Na³ )
•  A/(Na³)
•  A/(Na² )

Solution
(a) In fcc lattice, the no. of atoms per unit cell - 4 Density=(mass of unit cell)/(volume of unit cell) =(4A/N)/a³ =4A/(Na³ )

Q8.A crystal has bcc structure and its lattice constant is 3.6 Å. What is the atomic radius?

•  3.6 Å
•  1.8 Å
•  1.27 Å
•  1.567 Å

Solution
(d) Atomic radius for bcc structure, r=(a√3)/4=(3.6√3)/4=1.56 Å

Q9.By increasing the temperature, the specific resistance of a conductor and a semiconductor

•  Increases for both
•   Decreases for both
•  Increases, decreases respectively
•  Decreases, increases respectively

Solution
(c)Increases, decreases respectively

Q10. Correct relation for triode is

•  μ=g_m×r_p
•  μ=g_m/r_p
•  μ=2g_m×r_p
•  None of these

Solution
(a)μ=g_m×r_p