ELECTRONICS-QUIZ 20

ELECTRONICS-QUIZ 20

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. Current gain of a transistor in common base mode is 0.95. Its value in common emitter mode is

•  0.95
•  1.5
•  19
•  (19)^-1

Solution
(c) β=α/(1-α)=0.95/(1-0.95)=0.95/0.05=19

Q2.In the following circuit of PN junction diodes D₁,D₂ and D₃ are ideal then i is

•  E/R
•  E/2R
•  2E/3R
•  Zero

Solution
(a) Diodes D₁ and D₃ are forward biased and D₂ is reverse biased so the circuit can be redrawn as follows ⇒i=E/R.

Q3. Which one of the following statement is not correct in the case of light emitting diodes

•  It is a heavily doped p-n junction
•  It emits light only when it is forward biased
•  It emits light only when it is reverse biased
•  The energy of the light emitted is less than the energy gap of the semiconductor used

Solution
(c)It emits light only when it is reverse biased

Q4. The ionic bond is absent in

•  NaCl
•  CsCl
•  LiF
•  H2O

Solution
(d) Ionic bond is a type of chemical bond based on electrostatic forces between two oppositely charged ions. Bond between NaCl, CsCl and LiF are ionic, while H2O forms a covalent bond.

Q5.Different voltages are applied across a p-n junction and the currents are measured from each value. Which of the following graphs is obtained between voltage and current?

•  
  
  
  
•  
  
  
  
•  
  
  
  
•  
  
  
  

Solution
(a) When the junction diode is forward biased, ie, p-side is kept at higher potential, the current in the diode changes with the voltage applied across the diode. The current increases very slowly till the voltage across the diode crosses a certain value. After this voltage, the diode current increases rapidly even for very small increase in the diode voltage. The current-voltage relation for diode is shown  

.  

Q6. In a diode valve, the state of saturation can be obtained easily by

•  High plate voltage and high filament current
•  Low filament current and high plate voltage
• Low plate voltage and high cathode temperature
•  High filament current and high plate voltage

Solution
(b)Low filament current and high plate voltage

Q7.The current gain of a transistor in a common emitter configuration is 40. If the emitter current is 8.2 mA, then base current is

•  0.02 mA
•  0.2 mA
•  2.0 mA
•  0.4 mA

Solution
(b)0.2 mA.

Q8.In a P-type semiconductor

•  Current is mainly carried by holes
•  Current is mainly carried by electrons
•  The material is always positively charged
•  Doping is done by pentavalent material

Solution
(a) In P-type semiconductors, holes are majority charge carriers

Q9.Bonding in a germanium crystal (semi-conductor) is

•  Metallic
•  Ionic
•  Vander Waal’s type
•  Covalent

Solution
(d) Covalent bonding exists in semi-conductor

Q10. The reverse bias in a junction diode is changed from 8 V to 13 V then the value of the current charges from 40 μA to 60 μA. The resistance of junction diode will be

•  2×10⁵ Ω
•  2.5×10⁵ Ω
•  3×10⁵ Ω
•  4×10⁵ Ω

Solution
(b)R_e=∆V/∆I=((13-8))/((60-40)×10^-6 )=2.5×10⁵ Ω.