CBSE Questions for Class 12 Engineering Physics Semiconductor Electronics: Materials,Devices And Simple Circuits Quiz 7 - MCQExams.com

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
Which of the following represents NAND gate ?
Calculate the plate resistance r$$_p$$ of the triode valve?
  • $$0.12$$ $$\times$$ $$10$$$$^4$$ ohm
  • $$1.2$$ $$\times$$$$ 10$$$$^4$$ ohm
  • $$1.3$$ $$\times$$ $$10$$$$^4$$ ohm
  • $$1.4$$ $$\times$$ $$10$$$$^4$$ ohm
If $${n}_{p}$$ and $${n}_{e}$$ are the number of holes and conduction electrons in an intrinsic semiconductor then _________.
  • $${n}_{p}> {n}_{e}$$
  • $${n}_{p}={n}_{e}$$
  • $${n}_{p}< {n}_{e}$$
  • $${n}_{p}\ne {n}_{e}$$
To get an output $$Y=1$$ in given circuit which of the following input will be correct.
306561.png
  • $$A=1; B=0; C=1$$
  • $$A=1; B=1; C=0$$
  • $$A=0; B=1; C=0$$
  • $$A=1; B=0; C=0$$
Electrical conduction in a semiconductor takes place due to
  • electrons only
  • holes only
  • both electrons and holes
  • neither electrons nor holes
The conductivity of a magnetic substance for the lines of force with respect to air is called the
  • Magnetic induction
  • Magnetic permeability
  • Magnetic flux density
  • Intensity of magnetisation
Different voltage are applied across a p-n junction and the currents are measured for each value. Which of the following graphs is obtained between voltage V and current i:
In an unbiased p-n junction, holes diffuse from the p-region to n-region because
  • Free electrons in the n-region attract them.
  • They move across the junction by the potential difference.
  • Hole concentration in p-region is more as compared to n-region.
  • All of the above.
When an intrinsic semiconductor is connected to an electric cell, the holes move towards the _________ terminal of the cell.
  • Holes, negative positive
  • Electron, negative
  • Electrons, positive
  • Both (1) and (3)
Diodes are used to ___________.
  • convert DC into AC
  • convert AC into DC
  • resistance control
  • current regulation
The width of the depleted region of a p-n junction is of the order of a few tenth of a ________.
  • millimeter
  • micrometer
  • metre
  • nanometre
n-type silicon is obtained by:
  • doping with tetravalent element
  • doping with pentavalent element
  • doping with trivalent element
  • doping with a mixture of trivalent and tetravalent current
The most widely used semiconductors are
(i) silicon  (ii) germanium
(iii) phosphorus   (iv) arsenic
  • (i) and (ii)
  • (ii) and (iii)
  • (iii) and (iv)
  • (i), (ii), (iv),(iii)
Which of the following doping will produce a p-type semiconductor?
  • Germanium with phosphorus
  • Silicon with germanium
  • Germanium with antomony
  • Silicon with indium
p-n junction is said to be forward bias. If
  • the n-side is connected to the -ve side and p-side to the +ve terminal of an external battery.
  • the n-side is connected to the +ve side and p-side to the -ve side of an external battery.
  • n-side is connected to +ve terminal and p-side in neutral.
  • none of these
Space charge region around a p-n junction:
  • does not contain mobile carriers
  • contains both free electrons and holes
  • contains one type of mobile carriers depending on the level of doping
  • contains electrons only as free carriers
In a p-type semiconductor majority charge carriers are _________.
  • holes
  • electrons
  • both holes and electrons
  • ions
The circuit given represents which of logic operations
432589.png
  • AND
  • NOT
  • OR
  • NOR
Which logic gates is represented by the following combination of logic gates?
432577.png
  • OR
  • NAND
  • AND
  • NOR
Identify the logic operation of the following logic circuit:
432618.png
  • NAND
  • AND
  • NOR
  • OR
The given truth table is for
InputInputOutput
ABY
$$0$$$$0$$$$1$$
$$0$$$$1$$$$1$$
$$1$$$$0$$$$1$$
$$1$$$$1$$$$0$$
  • AND gate
  • OR gate
  • NAND gate
  • NOR gate
The real time variation of input signals $$A$$ and $$B$$ are as shown below. If the inputs are fed into NAND gate, then select the output signal from the following.
432622.png
As we are growing in technology, use of wires in an electrical circuit is reducing. This is done by using semiconductor chips or reducing length of wire as much as possible. What could be the possible reason for the above? 
  • Using chips allows more compact devices
  • Heat loss in wires is reduced
  • Power requirements are reduced
  • All of the above
When the two inputs of a NAND gate are shorted, the resulting gate is :
  • NOR
  • OR
  • NOT
  • AND
The delpetion layer in a p-n junction diode is $$10^{-6}m$$ wide and its knee potential is $$0.5V$$, then the inner electric field in the depletion region is:
  • $$5\times 10^{6}V/m$$
  • $$5\times 10^{-7}V/m$$
  • $$5\times 10^{5}V/m$$
  • $$5\times 10^{-1}V/m$$
If the band-gap between valence band and conduction band in a material is $$5.0\ eV$$, then the material is a/an
  • semiconductor
  • good conductor
  • superconductor
  • insulator
The input to the digital circuit are as shown below. The output Y is:
461142.PNG
  • $$A+B+\overline{C}$$
  • $$(A+B)\overline{C}$$
  • $$\overline{A}+\overline{B}+\overline{C}$$
  • $$\overline{A}+\overline{B}+C$$
In the energy band diagram of a material shown below, the open circles and filled circles denote holes and electrons respectively. The material most likely is a/an
459279.jpg
  • p-type semiconductor
  • insulator
  • metal
  • n-type semiconductor
Which logic gate is represented by the following combination of logic gates?
467237.png
  • OR
  • NOR
  • AND
  • NAND
The part of a transistor which is heavily dopped to produce a large number of majority carriers is:
  • Base
  • Emitter
  • Collector
  • None of these
How many NAND gates are required to form an AND gate?
  • $$1$$
  • $$2$$
  • $$3$$
  • $$4$$
Which type of gate the following truth table represents?
InputInputOutput
$$A$$$$B$$$$Q$$
$$0$$$$0$$$$1$$
$$0$$$$1$$$$1$$
$$1$$$$0$$$$1$$
$$1$$$$1$$$$0$$
  • NOT
  • AND
  • OR
  • NAND
Fill in the blank.
The following truth table with $$A$$ and $$B$$ as inputs is for _________ gate.
ABOutput
101
110
011
000
  • AND
  • OR
  • XOR
  • NOR
In a semiconductor
  • There are no free electrons at any temperature
  • The number of free electrons is more than that of the conductor.
  • There are no free electrons at $$0K$$
  • None of these
The output $$Y$$ of the logic circuit given above is:
461965.jpg
  • $$\bar { A } +B$$
  • $$\bar { A } $$
  • $$\overline { \left( \bar { A } +B \right) } \cdot \bar { A } $$
  • $$\overline { \left( \bar { A } +B \right) } \cdot A$$
If a rod has resistance 4 ohm and if rod is turned as half circle, then the resistance along diameter is
  • 1.56 ohm
  • 2.44 ohm
  • 4 ohm
  • 2 ohm
The follwoing combined logic gate diagram is eqivalent to
468964.jpg
  • NOR gate
  • OR gate
  • AND gate
  • NAND gate
Which logic gate produced 'LOW' output when any of the inputs is 'HIGH'?
  • AND
  • OR
  • NAND
  • NOR
In a $$p-n$$ junction photocell, the value of photoelectromotive force produced by monochromatic light is proportional to
  • The voltage applied at $$p-n$$ junction
  • The barrier voltage at $$p-n$$ junction
  • The intensity of light falling on cell
  • The frequency of light falling on cell
The truth tables of logic gates A, B, C, D are given here. Identify them correctly.
475028.jpg
  • A:  OR, B:  AND, C:  NOR, D:  NAND
  • A:  OR, B:  NOR, C:  AND, D:  NAND
  • A:  AND, B:  OR, C:  NAND, D:  NOR
  • A:  OR, B:  NOR, C:  NAND, D:  AND
Of the following NAND gate is :
In the following circuit the output Y becomes zero for the input combinations:
475030_20a682de7aa543b4bd725ca2b1bed15a.png
  • A=1, B=0, C=0
  • A=0, B=1, C=1
  • A=0, B=0, C=0
  • A=1, B=1, C=0
The rating of a zener diode is $$1 W, 15 V$$. Find the zener maximum current. 
  • $$66.7 A$$
  • $$1 A$$
  • $$15 A$$
  • $$66.7 mA$$
Which of the following logic expressions represents the logic diagram shown ?
508057_8e666fd83a704d5bacf95f339ed97241.png
  • $$X = A\overline B + \overline A B$$
  • $$X = \overline {AB} + A B$$
  • $$X = \overline {AB} + \overline A \overline B$$
  • $$X = \overline A\overline B + A B$$

Find the maximum zener current for the zener diode as shown in figure. Given, $$V_Z=6 V, R_Z=1.5 \Omega,  R=400 \Omega $$
507051_a10e5151f11045c6981e20efade10678.png
  • $$35.00 mA$$
  • $$30.87 mA$$
  • $$34.87 mA$$
  • $$34.87 A$$
A zener diode can be used as 
  • oscillator .
  • voltage regulator.
  • rectifier.
  • transformer.
A $$7.2 V$$ zener diode $$(7.2 V$$ at $$  20^oC) $$ has a positive temperature coefficient of $$0.0007 /^oC$$. What is the zener voltage at $$45^oC$$ ?
  • $$7.20 V$$
  • $$7.33 V$$
  • $$7.13 V$$
  • $$6.36 V$$
Across the depletion region, there is a barrier potential which 
  • prevents the movement of electron from the n region into the p region
  • prevents the movement of electron from the p region into the n region
  • prevents the movement of holes from the n region into the p region
  • prevents the movement of holes from the p region into the n region
Which of the following is/are true regarding  breakdown voltage of Zener diode?
  • If the reverse bias voltage across a p-n junction diode is increased, at a particular voltage the reverse current suddenly decreases to a large value
  • The holes in the n-side and the conduction electrons in the p-side are accelerated due to the reverse bias voltage.
  • The voltage at which the rate of creation of hole-electron pairs is increased leading to the increased current is called avalanche breakdown
  • None of the above
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