CBSE Questions for Class 12 Engineering Physics Semiconductor Electronics: Materials,Devices And Simple Circuits Quiz 11 - MCQExams.com

The I -V characteristic of an LED is:
The impurity atoms needed to make a p-type semiconductor are
  • phosphorus
  • boron
  • antimony
  • arsenic
In the depletion layer, the electric field created
  • is from n-side to p-side
  • is from p-side to n-side
  • changes randomly
  • depends on the biasing
The dominant mechanisms for motion of charge carriers in forward and reversed biased silicon p-n junctions are :
  • Diffusion in forward bias, drift in reverse bias
  • Diffusion in both forward and reverse bias
  • Drift in both forward and reverse bias
  • None of these
Which of the following circuits correctly represents the following truth table?
1013169_622b335fafde4a84bf73c93af1362d4c.png
A zener regulated power supply consists of a $$9 V $$ battery connected in series with a and a zener diode. The zener diode maintains a constant voltage drop of $$4V $$ The current drawn by the load resistance will be :
  • $$0.025 A$$
  • $$0.050 A$$
  • $$0.01 A$$
  • $$0.015 A$$
In which of the following circuits is the diode forward biased?
The dominant mechanisms of motion of change carriers in forward and reverse biased silicon $$P-N$$ junction are
  • drift in forward bias, diffusion in reverse bias
  • diffusion in forward bias, drift in reverses bias
  • diffusion in both forward and reverse bias
  • drift in both forward and reverse bias
A non-conducting device is connected in a series circuit with a battery and a resistance. A current is found to pass through the circuit. If the polarity of the battery is reversed, the current drops to almost zero. The device may be
  • a p-n junction diode
  • an intrinsic semiconductor
  • a p-type semiconductor
  • a n-type semiconductor

 If the resistivity of an alloy is $$\rho '$$ and that of constituent metal is $$\rho $$ then :
  • $$\rho ' > \rho $$
  • $$\rho ' < \rho $$
  • $$\rho ' = \rho $$
  • there is no simple reaction between $$\rho '\& \rho $$
If a p-n junction diode is reverse biased, then the resistance measure by an ohm-meter will be
  • zero
  • low
  • high
  • infinite
In the case of forward biasing of a p-n junction diode,which one of the following figure correctly depicts the direction of conventional current?
A Zener diode is connected to a battery and a load as shown below: The current $$I,I_{Z}$$ and $$I_{L}$$ are respectively :
1076098_28dd10ecc1bb40a3963af8092092ecd9.png
  • $$12.5\ mA,735\ mA,5\ mA$$
  • $$12.5\ mA,5\ mA,7.5\ mA$$
  • $$15\ mA,7.5\ mA,7.5\ mA$$
  • $$15\ mA,5\ mA,10\ mA$$
In a pure silicon $$()$$ crystal at $$300 K, 10^{21}$$ atoms of phosphorus are added per cubic meter. The new hole concentration will be:-
  • $$10^{21} \text{per} \ m^3$$
  • $$10^{19} \text{per} \ m^3$$
  • $$10^{11} \text{per} \ m^3$$
  • $$10^{5} \text{per} \ m^3$$
The following combination of gates is equivalent to :
1115513_8ef958411ee74ffca0019032f621fe32.png
In an unbiased PN-junction,
  • The junction current at equilibrium is zero as charges do not cross the junction
  • The junction current reduces with rise in temperature
  • The junction current at equilibrium is zero as equal but opposite carriers are crossing the junction
  • The junction current is due to minority carriers only 
For a purely resistive circuit, which of the following statements is incorrect?
  • rms current will vary if the frequency of the source is varied
  • Power factor is equal to $$1$$
  • Current and voltage are in phase
  • The average Power dissipated through the resistor is directly proportional to $${i}_{rms}^{2}$$
Which is not true:
  • Resistance of metals increases with increasing temperature
  • Resistance of semi-conductors decreases with rise of temperature
  • Resistance of an electrolyte increases with rise of temperature
  • None of the above
The combination of the gates shown will produce
1131718_30cbf4e10e7b4e1a90eba835ef90ea60.png
  • AND gate
  • NAND gate
  • NOR gate
  • XOR gate
In a P-type semiconductor, the acceptor level is $$57meV$$, above the valence band. The maximum wavelength of light required to produce a hole will be 
  • $$57 \mathrm { A } ^ { o }$$
  • $$57 \times 10 ^ { - 3 } A ^ { o }$$
  • $$2.18\times10 ^ { -5 }A^o$$
  • $$11.61 \times 10 \mathrm { A } ^ { \circ }$$
In the following circuits, PN-junction diodes Dl, D2 and D3 are ideal for the following potential of AB, the correct increasing order of resistance between A and B will be - 
1168429_14b29b57d73d488280bb2944da54d8ea.png
  • $$( i ) < ( i i ) < ( i i i )$$
  • $$\text { (iii) } < \text { (ii) } < \text { (i) }$$
  • $$\text { (ii) } = \text { (iii) } < \text { (i) }$$
  • $$\text { (i) } = \text { (iii) } < \text { (ii) }$$
Find current through the ideal diode.
1566205_bff710290d2742229ecbd58ec9ffa976.png
  • Zero
  • 20A
  • 0.05 A
  • 0.15 A
The output Y of the combination of gates shown is equal to:
1131752_ed91a97b276d49e284f30c0576b9e03a.png
  • A
  • $$\bar { A } $$
  • A+B
  • AB
In a silicon diode, the reverse current increases from $$10\mu A$$ to $$20\mu A$$. when the reverse voltage change from $$2V$$ to $$4V$$. The reverse ac resistance of the diode is
  • $$2\times 10^{5}\ \Omega$$
  • $$1\times 10^{5}\ \Omega$$
  • $$3\times 10^{5}\ \Omega$$
  • $$4\times 10^{5}\ \Omega$$
How many NOR gates are required to form NAND gate:
  • $$1$$
  • $$3$$
  • $$2$$
  • $$4$$
A two inputed XOR gate produces an high output only when its both inputs are:
  • same
  • different
  • low
  • high
When all the inputs of a NAND gate are connected together, the resulting circuit is:
  • a NOT gate
  • an AND gate
  • an OR gate
  • a NOR gate
Select the correct statement from the following 
  • a diode can be used as a rectifier
  • a diode cannot be used as a rectifier
  • the current in a diode is always proportional to the applied voltage
  • None of these
In a zener diode, break down occurs in reverse bias due to
  • Impact ionisation
  • Internal field emission
  • High doping concentration
  • All of these
The probability of  electrons to be found in the conduction band of an intrinsic semiconductor at a finite temperature :-
  • decreases exponentially with increasing band gap
  • increases exponentially with increasing band gap
  • decreases with increasing temperature
  • is independent of the temperature and the band gap
A.P.N junction Diode when connected to an AC sourice behaves as an ?
  • Rectifier
  • Zero resistance
  • Amplifier
  • None of these
If electromagnetic rays are incident on a semiconductors its conductivity .
  • Increases
  • Increases with increases frequency
  • Increases when frequency increases above certain frequency
  • Increases when wavelength is increases above a certain wavelength
In the circuit given the current through the Zener diode is :- -
1171493_022e0633081f4325947cac2667e31d59.png
  • $$10 \mathrm { mA }$$
  • $$6.67 \mathrm { mA }$$
  • $$5 \mathrm { mA }$$
  • $$3.33 \mathrm { mA }$$
In an intrinsic semiconductor, the density of conduction electrons is $$7.07\times 10^{15}m^{-3}$$. When it is doped with indium, the density of holes becomes $$5\times 10^{22}m^{-3}$$. Find the density of conduction electrons in doped semiconductor 
  • $$Zero$$
  • $$1\times 10^9m^{-3}$$
  • $$7\times 10^{15}m^{-3}$$
  • $$5\times 10^{22}m^{-3}$$
When a diode is heavily doped the 
  • Zener voltage will be low
  • Avalanche voltage will be high
  • Depletion region will be thin
  • Leakage current will be low
In the adjacent circuit, A and B represent two inputs and C represents the output. The circuit represents.

1205389_3d70953264f14162bcac82bf38994574.jpg
  • NOR gate
  • AND gate
  • NAND gate
  • OR gate
A light emitting diode (LED) has a voltage drop of 2 V across it and passes a current of 10 mA. When it operates with a 6 V battery through a limiting resistor R, the value of R is 
  • 200 $$\Omega$$
  • 400 $$\Omega$$
  • 40 $$k\Omega$$
  • 4 $$k\Omega$$
The mobility of hole in a semiconductor depend on
  • Electric field
  • Potential difference
  • current
  • Mass
If potential $$V=100\pm0.5$$Volt and current $$I=10\pm0.2$$ amp are given to us, then what will be the value of resistance
  • $$10\pm0.7$$ohm
  • $$5\pm2$$ohm
  • $$0.1\pm0.2$$ohm
  • none of these
A zener diode, having breakdown voltage equal to 15 V is used in a voltage regulator circuit shown in figure. The current through the diode is

1213916_079828a76e58426fabcc08c5baea648b.jpg
  • 20 mA
  • 5 mA
  • 10 mA
  • 15 mA
For detecting intensity of light we use
  • Photodiode in forward bias
  • Photodiode in reverse bias
  • LED in forward bias
  • LED in reverse bias
The material used in solar cells contains
  • $$C_s$$
  • $$Si$$
  • $$Sn$$
  • None of the above
Which of the following statements is true for a p-n-p transistor when used in an amplifier circuit ?
  • Emitter is connected to negative terminal of a battery.
  • Base current is always lower than emitter current.
  • Collector is connected to positive terminal of a battery
  • Collector current is always more than the emitter current
The number of particles crossing unit area perpendicular to X-axis in unit time is given by $$ \dfrac { D\left( n_ 2-n_ 1 \right)  }{ \left( x_ 2-x_ 1 \right)  }  $$ where $$ n_1 and n_2 $$ are number of particle per unit volume respectively at and $$ x_2 $$ The dimension of the diffusion constant D are
  • $$ \left[ LT^ { -1}  \right] $$
  • $$ \left[ L^2 T^ { -1} \right] $$
  • [LT]
  • $$ [L^{-1} T ] $$
The relation between dynamic plate resistance $$\left( r _ { p } \right)$$ of a vacuum diode and plate current in the space charge limited region, is 
  • $$r _ { p } \propto I _ { p }$$
  • $$r _ { p } \propto I _ { p } ^ { 3 / 2 }$$
  • $$r _ { p } \propto \dfrac { 1 } { I _ { p } }$$
  • $$r _ { p } \propto \dfrac { 1 } { \left( I _ { p } \right) ^ { 1 / 3 } }$$
Which of the following break down of pn junction is reversible?
  • Avalanche breakdown
  • Zener breakdown
  • Dielectric breakdown
  • All of these
A gate in which all the inputs must be low to get a high output is called
  • NAND gate
  • An inverter
  • NOR gate
  • AND gate
The given figure shows the waveforms for three inputs $$A,B $$ and $$C$$ and that for the output $$Y$$ of a logic circuit. The logic circuit is  
1285971_7005149338114458b3a7f8277c1c9e3a.png
  • $$XOR$$ Gate
  • $$XNOR$$ Gate
  • $$NAND$$ Gate
  • $$NOR$$ Gate
In PN-junction diode the reverse saturation current is $$10 ^ { - 5 }$$ amp at $$27 ^ { \circ } C$$. The forward current for a voltage of 0.2 volt is
  • $$2037.6 \times 10 ^ { - 3 } \mathrm { amp }$$
  • $$203.76 \times 10 ^ { - 3 } \mathrm { amp }$$
  • $$20.376 \times 10 ^ { - 3 }amp$$
  • $$2.0376 \times 10 ^ { 3 }amp$$
The magnitude of the force between a pair of conductors, each of length 110 cm, carrying a current of 10 A and separated by a distance of 10 cm is
  • $$55 \times 10 ^ { - 5 } N$$
  • $$44 \times 10 ^ { - 5 } N$$
  • $$33 \times 10 ^ { - 5 } N$$
  • $$22 \times 10 ^ { - 5 } N$$
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