CBSE Questions for Class 12 Engineering Physics Semiconductor Electronics: Materials,Devices And Simple Circuits Quiz 8 - MCQExams.com

When a forward bias is applied to p-n junction it:
  • Raises the potential barrier.
  • Reduces the majority carrier current to zero.
  • Lowers the potential barrier.
  • None of the above.
In a n - type semi conductors which of the following statement is true:
  • Electrons are majority carrier and trivalent impurity are the dopants.
  • Electrons are minority carrier and pentavalent atoms are dopants.
  • Holes are minority carrier and pentavalent atoms are dopants.
  • Holes are majority carrier and trivalent atoms are the dopants.
The conductivity of a semi conductor is:
  • Greater than the conductivity of metals.
  • Less than the conductivity of metals.
  • Equal to the conductivity of metals.
  • Intermediate between the conductivity of metals and insulators.
Resistance of a wire is r ohm. The wire taken is double its length, then its intial resistance in ohm will be
  • $$\dfrac{r}{2}$$
  • $$4r$$
  • $$2r$$
  • $$\dfrac{r}{4}$$
The attached figure shows the characteristics of:
552377.jpg
  • Zener diode
  • Avalanche diode
  • Photodiode
  • LED
The conductivity of a semi conductor can be increased by:
  • Heating the semi conductor
  • Doping the semi conductor
  • Both (a) and (b)
  • None
A Zener diode having break-down voltage $$5.6V$$ is connected in reverse bias with a battery of emf $$10V$$ and a resistance of $$100\Omega$$ in series. The current flowing through the Zener is
  • $$88mA$$
  • $$0.88mA$$
  • $$4.4mA$$
  • $$44mA$$
A NOR gate and a NAND gate are connected as shown in the figure. Two different sets of inputs are given to this set up. In the first case, the input to the gates are A=0, B=0, C=In the second case, the inputs are A=1, B=0, C=The output D in the first case and second case respectively are
574281.PNG
  • 0 and 0
  • 0 and 1
  • 1 and 0
  • 1 and 1
Energy band gap between valence band and conduction band for insulator is:
  • Zero
  • greater than $$9\ eV$$
  • less than conductors
  • approximately $$1\ eV$$
Energy band gap between valence band and conduction band for conductor is:
  • more than semiconductors
  • Zero
  • more than insulators
  • None of these
Conductors are materials having an electrical conductivity :
  • greater than $$10^3$$ S/cm
  • between $$10^{-8}\ to \ 10^3$$ S/cm
  • equal to $$10^{-8}$$ S/cm
  • Zero
The output of an OR gate is connected to both the inputs of a NAND gate. The combination will serve as:
  • AND gate
  • NOT gate
  • NAND gate
  • NOR gate
Semiconductors are materials having an electrical conductivity :
  • Less than insulators
  • between $$10^{-8}\ S/cm \ to \ 10^3\ S/cm$$
  • Equal to zero
  • Greater than $$10^3\ S/cm$$
Insulators are materials having an electrical conductivity equal to:
  • Between $$10^{-8}$$ S/cm to $$10^{3}$$ S/cm
  • $$<\ 10^{-8}$$ S/cm
  • Equal to $$ 10^{3}$$ S/cm
  • $$>\ 10^{3}$$ S/cm
A proper combination of $$3$$ NOT and $$1$$ AND gates is shown. If $$A=0$$, $$B=1$$, $$C=1$$ then the output of this combination is
579976_727c33d7880748ddbfd30fc33d9ad0d3.png
  • $$1$$
  • Zero
  • Not predictable
  • None of these
Which of the following is a property of a Light Emitting Diode (LED)?
  • Low Threshold Voltage and High Reverse Breakdown Voltage
  • High Threshold Voltage and High Reverse Breakdown Voltage
  • High Threshold Voltage and Low Reverse Breakdown Voltage
  • Low Threshold Voltage and Low Reverse Breakdown Voltage

The addition of pentavalent impurities  ________ of the semiconductor.
  • brings no change to the conductivity
  • decreases the conductivity
  • increases the conductivity
  • reduces the formation of free electrons
What change could be seen when dopant atoms are added to an intrinsic semiconductor?
  • It will change the proton and hole carrier concentrations of the semiconductor
  • It will change the temperature of the semiconductor
  • It will change the electron and hole carrier concentrations of the semiconductor
  • It will decrease the formation of free electrons in the semiconductor
The curve represents the $$I-V$$ characteristics of which optoelectronic device?
580901_eceb13acd2be4a838f2f6fca3854b48f.png
  • Solar Cell
  • Photo-diode
  • Light Emitting Diode (LED)
  • None of these
The semiconductor diodes in which carriers are generated by photons (photo-excitation) are called            devices.
  • thermo-optic
  • optical
  • optoelectronic
  • thermi-ionic
Energy band gap between valence band and conduction band for semiconductor is:
  • approximately 1 eV
  • less than conductors
  • equal to conductors
  • more than insulator
Match the following
a) p-type semiconductor1) Pure semiconductor
b) Intrinsic semiconductor2) Doped with impurity
c) Extrinsic semiconductor3) majority carriers are electrons
d) n-type semiconductor4) majority carriers are holes
  • a-3,b-2,c-4,d-1
  • a-1,b-2,c-4,d-3
  • a-4,b-1,c-2,d-3
  • a-2,b-1,c-4,d-3
What is the reason to operate the photodiodes in reverse bias? 
  • fractional change due to the photo-effects on the majority carrier dominated forward bias current is more easily measurable than the fractional change in the reverse bias current.
  • reverse bias is more efficient than forward bias.
  • fractional change due to the photo-effects on the minority carrier dominated reverse bias current is more easily measurable than the fractional change in the forward bias current.
  • reverse bias configuration result in larger amount of current (in $$\mu A$$)
Examples of opto-electronic devices are 
  • Light Emitting Diodes (LED)
  • Zener diode
  • Solar cells
  • Photodiodes
The junction area is kept much larger in a solar cell
  • for solar radiation to be incident because we are interested in more power.
  • for solar radiation to be incident because we are interested in less power.
  • for solar radiation to be properly reflected from the junction.
  • None of these.
The drift current in a $$p-n$$ junction diode is
  • motion of charge carriers due to the electric field
  • motion of charge carriers due to the charge concentration gradient
  • in same direction as the diffusion current
  • opposite in direction to the diffusion current
The process that occur during formation of a $$p-n$$ junction is
  • diffusion
  • doping
  • drift
  • depletion
The material selected for solar cell fabrication has
  • band gap ($$1.0$$ to $$1.8\ eV$$)
  • high optical absorption ($$10^4 \ cm^{-1}$$)
  • electrical conductivity
  • band gap ($$0.4$$ to $$1.\ eV$$)
The space-charge region on either side of the junction together is known as depletion region because 
  • neither electrons nor holes exist in this region.
  • the electrons and holes taking part in the initial movement across the junction freed the region of its free charges.
  • the electrons and holes in this region are immobile.
  • None of these
In                 ,  excess minority carriers recombine with majority carriers near the p-n junction.
  • Photodiode
  • Light Emitting Diode
  • Solar Cells
  • Zener diode
During the formation of $$p-n$$ junction, 
  • holes diffuse from $$p-$$side to $$n-$$side ($$p \rightarrow n$$)
  • electrons diffuse from $$p-$$side to $$n-$$side ($$p \rightarrow n$$)
  • electrons diffuse from $$n-$$side to $$p-$$side ($$n \rightarrow p$$)
  • holes diffuse from $$n-$$side to $$p-$$side ($$n \rightarrow p$$)
The I V characteristics of solar cell is drawn in the fourth quadrant of the coordinate axes because 
  • a solar cell does not draw current but supplies the same to the load.
  • a solar cell draws current but supplies no current to the load.
  • a solar cell draws voltage and supplies current to the load
  • a solar cell draws current but supplies voltage to the load
Due to the concentration gradient across p-, and n- sides, the motion of charge carries gives rise to_______ current across the junction
  • drift
  • diffusion
  • both diffusion and drift
  • None of these
When an external voltage ($$V$$) is applied across the diode in reverse bias with a barrier potential of $$V_o$$, the effect barrier height under reverse bias is 
  • $$V_o + V$$
  • $$V_o - V$$
  • $$V - V_o$$
  • None of these
 The thickness of depletion region is of the order of 
  • $$0.1 \mu m$$
  • $$1 \mu m$$
  • $$0.1 mm$$
  • $$1 mm$$
When an external voltage $$V$$ is applied across a semiconductor diode such that $$p-$$side is connected to the positive terminal of the battery and $$n-$$side to the negative terminal, it is said to be
  • reverse biased.
  • forward biased.
  • bias free.
  • None of these
In the figure, the numbers 1, 2, 3 represent barrier potential ($$V_o$$) of a p-n junction under forward bias
581240.JPG
  • 1 - high voltage battery 2 - without battery 3 - low voltage bettery
  • 1 - high voltage battery, 2 - low voltage battery, 3 - without battery
  • 1 - without battery, 2 - low voltage battery, 3 - high voltage battery
  • 1 - low voltage battery 2 - without battery 3 - high voltage bettery
In this $$I-V$$ characteristic curve of a zener diode, regions 1 and 2 respectively indicate
581269_043600d625cf4a168c62d6206a8778e6.png
  • forward bias and reverse bias regions.
  • reverse bias and forward bias regions.
  • forward bias regions only.
  • reverse bias regions only.
Which of the following is an example of an indirect band gap intrinsic semiconductor?
  • Silicon
  • Germanium
  • Gallium Arsenide
  • None of these
For creating a $$p-n$$ junction, 
  • we take one slab of p-type semiconductor and physically join it to another n-type semiconductor
  • continuous contact at the atomic level is necessary.
  • two macroscopic smooth flat slabs can be used
  • None of these
 The direction of the applied voltage ($$V$$) is opposite to the built-in potential $$V_o$$ .  The effective barrier height under forward bias is
  • ($$V_o + V$$).
  • ($$V_o V$$).
  • ($$V V_o$$).
  • ($$V_o \times V$$).
The logic circuit as shown below has the input wave forms $$A$$ and $$B$$ as shown. Pick out the correct output waveform.
583997_ef9b3ed4d19f4333b5bbacaa3e787a91.JPG
By adding certain impurities to                   in the appropriate concentrations the conductivity can be well-controlled.
  • semiconductors
  • conductors
  • insulators
  • superconductors
Which of the following statement(s) is/are true?
  • A hole is an electric charge carrier with a positive charge, equal in magnitude but opposite in polarity to the charge on the electron
  • A hole is the absence of an electron in a particular place in an atom
  • A hole is an electric charge carrier with a negative charge
  • none of these
The logic behind NOR gate is that which gives
  • high output when both inputs are high
  • low output when both inputs are low
  • high output when both inputs are low
  • none of these
The diagram of a logic circuit is given below, the output of the circuit is represented by
596115_8b0c0c56768743bb8afb4927b87e3ed6.png
  • W+(X+Y)
  • W+(X.Y)
  • W.(X+Y)
  • W.(X.Y)
Electrons always moves from
  • Valance band to conduction band
  • Conduction to valance band
  • Some times from valance band to conduction and sometimes from conduction band to valance band
  • None of the above
In the following circuit, the output Y for all possible inputs A and B is expressed by the truth table
596139.jpg
When you have a P-N junction and you connect it to a DC voltage, this will lead 
  • The electrons near to the gap between the P-N junction from the N type material to move to the P side
  • The lack of electrons in the N type side will lead to have a holes
  • The holes near to the gap between the P-N junction from the P type material to move to the N side
  • Both A and C
The truth table of the combination of the logic gates shown in the figure is
586457_0516a1f0c23c4694918aefffe121605c.png
0:0:1


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