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

The I -V characteristic of an LED is:
The correct relationship between the two current gains $$\alpha \quad and\quad \beta $$ in a transistor is
  • $$\beta =\dfrac { \alpha }{ 1+\alpha } $$
  • $$\alpha =\dfrac { \beta }{ 1-\beta } $$
  • $$\alpha =\dfrac { \beta }{ 1+\beta } $$
  • $$\alpha =\dfrac { 1+\beta }{ \beta } $$
The impurity atoms needed to make a p-type semiconductor are
  • phosphorus
  • boron
  • antimony
  • arsenic
The part of a transistor which is heavily doped to produce a large number of majority carries is
  • base
  • emitter
  • collector
  • none of these
Which of the following circuits correctly represents the following truth table?
1013169_622b335fafde4a84bf73c93af1362d4c.png
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
Which is the correct diagram of a half-wave rectifier?
In a common base amplifier circuit, calculate the change in base current if that in the emitter current is $$2$$ mA and $$\alpha =0.98$$.
  • $$0.04$$ mA
  • $$1.96$$ mA
  • $$0.98$$ mA
  • $$2$$ mA

 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 $$\rho '\& \rho $$
The current gain of a transistor in a common-emitter circuit isThe ratio of emitter current to base current is
  • 40
  • 41
  • 42
  • 43
If a p-n junction diode is reverse biased, then the resistance measure by an ohm-meter will be
  • zero
  • low
  • high
  • infinite
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 
Consider an NPN transistor amplifier in common-emitter configuration. The current gain of the transistor is $$100$$. If the collector current changes by $$1$$ mA, what will be the change in emitter current?
  • $$1.1$$ mA
  • $$1.01$$ mA
  • $$0.01$$ mA
  • $$10$$ mA
In NPN transistor the collector current is $$10$$ mA. If $$90\%$$ of electrons emitted reach the collector, then?
  • Emitter current will be $$9$$ mA
  • Emitter current will be $$11.1$$ mA
  • Base current will be $$0.1$$ mA
  • Base current will be $$0.01$$ mA
A crystal diode is a 
  • Non-linear device
  • Amplifying device
  • Linear device
  • fluctuating device
The value of form factor in case of half wave rectifier is:
  • $$1.11$$
  • $$1.57$$
  • $$1.27$$
  • $$0.48$$
The following combination of gates is equivalent to :
1115513_8ef958411ee74ffca0019032f621fe32.png
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
The combination of the gates shown will produce
1131718_30cbf4e10e7b4e1a90eba835ef90ea60.png
  • AND gate
  • NAND gate
  • NOR gate
  • XOR gate
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
  • $$( i ) < ( i i ) < ( i i i )$$
  • $$\text { (iii) } < \text { (ii) } < \text { (i) }$$
  • $$\text { (ii) } = \text { (iii) } < \text { (i) }$$
  • $$\text { (i) } = \text { (iii) } < \text { (ii) }$$
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
  • $$1\times 10^{5}\ \Omega$$
  • $$3\times 10^{5}\ \Omega$$
  • $$2\times 10^{5}\ \Omega$$
  • $$4\times 10^{5}\ \Omega$$
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
A transistor has an $$\alpha = 0.95$$. It has change in emitter current of $$100$$ milliampere. Then the change in collector current is:-
  • $$100$$ milliampere
  • $$100.95$$ milliampere
  • $$99.05$$ milliampere
  • $$95$$ milliampere
In He-Ne laser, metastable state exists in: 
  • He
  • Ne
  • Both (1) & (2)
  • Neither He nor Ne
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 
  • $$Zero$$
  • $$1\times 10^9m^{-3}$$
  • $$7\times 10^{15}m^{-3}$$
  • $$5\times 10^{22}m^{-3}$$
A.P.N junction Diode when connected to an AC sourice behaves as an ?
  • Rectifier
  • Zero resistance
  • Amplifier
  • 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
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 the following common emitter circuit if $$\beta=100,V_{CE}=7V,V_{BE}=Negligible,R_C=2k\Omega,$$ then $$I_B=?$$
1174404_49ee90d41c5643fea68784e2ebdebcc6.PNG
  • $$0.01mA$$
  • $$0.04mA$$
  • $$0.02mA$$
  • $$0.03mA$$
In a resistor circuit shown here the base current is $$35mA.$$ The value of the resistor $$R_b$$ is
1208222_1f6a646b67134d5a8f2631538b4aeba9.png
  • $$300KW$$
  • $$450KW$$
  • $$257KW$$
  • $$500KW$$
Transistor with $$CE$$ configuration can be used as
  • AND gate
  • OR gate
  • NOR gate
  • NOT gate
Zener diode is used as-
  • Half wave rectifier
  • Full wave rectifier
  • A.C. voltage stabllizer
  • D.C. voltage stabilizer
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
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
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
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
  • $$2037.6 \times 10 ^ { - 3 } \mathrm { amp }$$
  • $$203.76 \times 10 ^ { - 3 } \mathrm { amp }$$
  • $$20.376 \times 10 ^ { - 3 }amp$$
  • $$2.0376 \times 10 ^ { 3 }amp$$
In the circuit shown in figure, the current gain $$\beta$$ = 100 for a npn transistor. The bias resistance $$R_B$$ so that $$V_{CE}$$ = 5V is ($$V_{BE}$$ < < 10 V)
1221266_44781cf5ba024040a46de0f9a304e8dd.png
  • $$2 \times 10^3 \ \Omega$$
  • $$10^5 \ \Omega$$
  • $$2 \times 10^5 \ \Omega$$
  • $$5 \times 10^5 \ \Omega$$
  • $$1 \times 10^3 \ \Omega$$
The intrinsic charge carrier density in germanium crystal at $$ 300 K is 2.5 \times 10^{13} / cm^3 $$. density in an n-type germanium crystal at 300 K be $$ 5 \times 10^{16} /cm^3 $$,the hole density in this n-type crystal at 300 K would be 
  • $$ 2.5 \times 10^{13} / cm^3 $$
  • $$ 5 \times 10^6 / cm^3 $$
  • $$ 1.25 \times 10^{10} / cm^3 $$
  • $$ 0.2 \times 10^4 / cm^3 $$
A voltage amplifier operated from a $$12$$ volt battery has a collector load $$6\ k\ \Omega$$. Calculate the maximum collector current in the circuit.
  • $$0.5\ mA$$
  • $$1\ mA$$
  • $$3\ mA$$
  • $$2\ mA$$
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 emitter base junction of a transistor is_____biased while the collector base junction is ____biased.
  • Reverse,forward
  • Reverse,reverse
  • Forward,forward
  • Forward,reverse
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
In a transistor the base is very lightly doped as compared to the emitter because by doing so
  • The flow across the base region is mainly because of holes.
  • The flow across the base region is mainly because of electrons.
  • Recombination is decreased in the base region.
  • Base current is high.
A common emitter amplifier circuit is shown in the figure below.For the transistor used in the circuit the current amplification factor, $${\beta _{dc}} = 100.other\;parameters\;are\;mentioned\;in\;the\;figure.$$
we find that:-
1292809_4da2a95f0eb94c3c876d5b22fc9f461e.png
  • $${v_{BE}} = + 18.2\;V,\;{V_{BC}} = - 3.45\;V\;and\;amplifier\;is\;working.$$
  • $${v_{BE}} = + 18.2\;V,\;{V_{BC}} = - 2.85\;V\;and\;amplifier\;is\;working.$$
  • $${v_{BE}} = + 18.2\;V,\;{V_{BC}} = - 3.75\;V\;and\;amplifier\;is\;working.$$
  • none
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