## Electronics Quiz-8

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. Consider the following statements A and B and identify the correct choice of the given answers A. The width of the depletion layer in a P-N junction diode increases in forward bias B. In an intrinsic semiconductor the fermi energy level is exactly in the middle of the forbidden gap
•  A is true and B is false
•  Both A and B are false
•  A is false and B is true
•  Both A and B are true
Solution
(c) In forward biasing of PN junction diode width of depletion layer decreases. In intrinsic semiconductor fermi energy level is exactly in the middle of the forbidden gap

Q2.Within depletion region of p-njunction diode
•  p-side is positive and n-side is negative
•  p-side is negative and n-side is positive
•  Both sides are positive or both negative
•  Both side are neutral
Solution
(b) In a p-n junction diode, electrons in conduction band on n-type side travel across the junction and leave the positively ionized impurity atoms unneutralised. Consequently, there is positively charged region adjacent to the junction in n-type material. On p-type side the electrons which have traversed the boundary recombine with positive holes in the valence bandand form a layer of unneutralised negatively ionised trivalent impurity atoms making a negatively charged region as shown in figure. The region around the junction is called charge depletion region or space charge region. Hence, within the depletion region, p-side is negative and n-side is positive.

Q3.  The introduction of a grid in a triode valve affects plate current by
•  Making the thermionic emission easier at low temperature
•  Releasing more electrons from the plate
•  Increasing plate voltage
•  Neutralizing space charge
Solution
(D)

Q4. In an unbiased p-n junction
•  Potential at p is more than that at n
•  Potential at p is less than that at n
•  Potential at p is equal to that at n
•  Potential at p is +ve and that at n is -ve
Solution
(b) Graph between potential and distance in a p-n junction diode is given by ∴potential at p is less than that at n.

Q5.In presence of interspace charge, at plate voltage of 200 V, the current is 80 mA. Then the current in mA at 400 V will be
•  160√2
•  2√2
•  80/√2
•  None of these
Solution
(a) I2/I1 =(V2/V1 )^(3/2) orI2=I1 (V2/V2)3/2 =80(400/200)^(3/2)=80×2√2=160√2

Q6. The cause of the potential barrier in a P-N diode is
•  Depletion of positive charges near the junction
•  Concentration of positive charges near the junction
• Depletion of negative charges near the junction
•  Concentration of positive and negative charges near the junction
Solution
(C)

Q7.Consider the following statement A and B and identify the correct choice of the given answers (A) A zener diode is always connected in reverse bias (B) The potential barrier of a PN junction lies between 0.1 to 0.3 V approximately
•  A and B are correct
•  A and B are Wrong
•  A is correct but B is wrong
•  A is wrong but B is correct
Solution
(D)

Q8.In circuit in following fig. the value of Y is

•  0
•  1
•  Fluctuates between 0 and 1
•  Indeterminate as the circuit can’t be realised
Solution
(a) Lower NOT gate inverts input to zero. NOT gate from NAND gate inverts this output to 1 upper NAND gate converts this input 1 and input 0 to 1. Thus A=1 and B=1 become inputs of NAND gate giving final output as zero. Choice A is correct

Q9.Resistance of a semiconductor
•  Increases with increase in temperature
•  Decreases with increase in temperature
•  Is not affected by change in temperature
•  Increase for germanium and decrease for silicon
Solution
(c) (b) The electric resistance of a typical intrinsic (non doped) semiconductor decreases exponentially with temperature R=R0e(Î±⁄T)

Q10. Ge and Si diodes conduct at 0.3 V and 0.7 V respectively. In the following figure if Ge diode connection is reversed, the value of V0 changes by

•  0.2 V
•  0.4 V
•  0.6 V
• 0.8 V
Solution
(b) Consider the case when Ge and Si diodes are connected as show in the given figure. Equivalent voltage drop across the combination Ge and Si diode =0.3 V ⇒ Current i=(12-0.3)/(5 kÎ©)=2.34 mA

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