CBSE Questions for Class 12 Medical Physics Semiconductor Electronics: Materials, Devices And Simple Circuits Quiz 5 - MCQExams.com

Which of the following is correct statement for voltage gain of n-p-n transistor in common emitter configuration?
  • $$A_V$$ increases continuously with increase in input voltage.
  • $$A_V$$ remains almost zero, then increases, decreases and again becomes zero with increase in input voltage.
  • $$A_V$$ is high, then decreases, then increases and becomes constant with increase in input voltage.
  • $$A_V$$ remains constant with increase in input voltage.
For detecting the light_______________.
  • The photodiode has to be forward biased
  • The photodiode has to be reversed biased
  • The LED has to connected in forward bias mode
  • The LED has to be connected in reverse bias mode
A logic gate is an electronic circuit which.
  • Makes logic decisions
  • Allows electron flow only in one direction
  • Works on binary algebra
  • Alternates between $$0$$ and $$1$$ values
  • None of the above
When a p-n junction diode is connected in forward bias its barrier potential
  • decreases and less current flows in the circuit
  • decreases and more current flows in the circuit
  • increases and more current flows in the circuit
  • decreases and no current flows in the circuit
The breakdown in a reverse biased p-n junction diode is more likely to occur due to.
  • large velocity of the minority charge if the doping concentration is small.
  • large velocity of the minority charge carriers if the doping concentration is small.
  • strong electric field in a depletion region if the doping concentration is small.
  • strong electric filed in the deplention region if the doping conentration is large.
Least doped region in a transistor is:
  • Either emitter or collector
  • Base
  • Emitter
  • Collector
The process by which ac is converted into dc is known as
  • Purification
  • Amplification
  • Rectification
  • Current Amplification
The nature of binding for a crystal with alternate and evenly spaced positive and negative ions is:
  • metallic
  • covalent
  • dipolar
  • ionic
Consider the following statements A and B and identify the correct answer.
Statement(A):A Zener diode is always connected in reverse bias to use it as voltage.
Statement(B):The potential barrier of a p-n 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.
A p-n junction diode cannot be used
  • as a rectifier.
  • for converting light energy to electric energy.
  • for getting light radiation.
  • for increasing the amplitude of an AC signal.
A full wave rectifier along with the output is shown in the given figure. The contributions from the diode $$(D_2)$$ are
15925_4732f6e2301a448999067146126a010c.PNG
  • C
  • A, C
  • B, D
  • A, B, C, D
A diode made of silicon has a barrier potential of $$0.7\ V$$ and a current of $$20\ mA$$ passes through the diode when a battery of emf $$3\ V$$ and a resistor is connected to it. The power dissipated across the resistor and diode are
  • $$0.046\ W, \ 0.014\ W$$
  • $$4.6\ W,\  0.14\ W$$
  • $$0.46\ W,\  0.14\ W$$
  • $$46\ W, \ 14\ W$$
AND gate
  • it has no equivalence to switching circuit.
  • it is equivalent to series switching circuit.
  • it is equivalent to parallel switching circuit.
  • it is a mixture of series and parallel switching circuit.
In a full-wave rectifier, the output is taken across a load resistor of $$800$$ ohm. If the resistance of diode in the forward biased condition is $$200$$ ohm, the efficiency of rectification of ac power into dc power is(in percentage)
  • $$64.96\%$$
  • $$40.6\%$$
  • $$81.2\%$$
  • $$80\%$$
A full wave p-n diode rectifier uses a load resistance of $$1300$$ $$\Omega$$. No filter is used. If the internal resistance of each diode is $$9$$ $$\Omega$$, then the efficiency of this full wave rectifier is
  • $$80.64\%$$
  • $$40.6\%$$
  • $$13.9\%$$
  • $$100\%$$
The output Y of the gate circuit shown in the fig is

16546.png
  • $$\bar{A}+\bar{B}$$
  • $$\overline{\bar A + \bar B}$$
  • $$\overline{A+B}$$
  • A + B
If the wavelength of light emitted when an electron fall from the first excited state to the ground state are $$\lambda$$, the wavelength of emitted radiation when an electron fall from meta-stable state to the ground state will be
  • greater than $$\lambda$$
  • less than $$\lambda$$
  • $$\lambda$$
  • cannot be determined
An n-p-n transistor conducts when
  • both collector and emitter are positive with respect to the base.
  • collector is positive and emitter is negative with respect to the base.
  • collector is positive and emitter is at same potential as the base.
  • both collector and emitter are negative with respect to the base.
Consider the following statements A and B and identify the correct answer:
A) germanium is preferred over silicon in the construction of Zener diode.
B) germanium has high thermal stability than silicon in the construction of Zener diode.
  • Both (A) and (B) are true.
  • Both (A) and (B) are false.
  • (A) is true but (B) is false.
  • (A) is false but (B) is true.
In an n-p-n transistor, the base and collector currents are $$100\ mu A$$ and $$9\ mA$$ respectively. Then the emitter current will be 
  • $$9.1\ mA$$
  • $$18.2\ mA$$
  • $$3.91\ mu A$$
  • $$18.2\ mu A$$
In the Boolean algebra: $$\overline{A+B}$$ is equal to:
  • A + B
  • $$\bar{\bar{A}}$$+$$\bar{\bar{B}}$$
  • $$\overline{\overline{A.B}}$$
  • $$\bar{A}$$ . $$\bar{B}$$
In a n-p-n transistor, the collector current is $$10 $$ mA. If $$10\%$$ of the electrons are lost in the base, then the emitter current is:
  • $$10 $$ mA
  • $$0.9 $$ mA
  • $$0.09 $$ mA
  • $$11.1$$ mA
Boolean expression $$Y = A.\bar{B} + B.\bar{A}$$ is given. If $$A = 1, B = 1$$ then $$Y =$$
  • 0
  • 1
  • 11
  • 10
For a CB amplifier current gain is $$0.54$$. If the emitter current is $$6.8\ mA$$, the collector current will be
  • $$1.7\ mA$$
  • $$2.7\ mA$$
  • $$3.7\ mA$$
  • $$4.7\ mA$$
A transistor has $$\alpha $$ $$=$$ $$0.95$$. If the emitter current is $$10\ mA$$, then the collector current will be
  • $$9.5\ mA$$
  • $$10\ mA$$
  • $$0.95\ mA$$
  • $$95\ mA$$
The change in emitter current by 2.1mA results in change of 2mA in the collector current and a change of 0.05V in the emitter base voltage. The input resistance is
  • 5K$$\Omega $$
  • 3K$$\Omega $$
  • 1K$$\Omega $$
  • 0.5K$$\Omega $$
If the collector current changes from $$2\ mA$$ to $$3\ mA$$ in a transistor when collector - emitter voltage is increased from $$2\ V$$ to $$10\ V$$, the output resistance is
  • $$1\ K$$$$\Omega $$
  • $$8\ K$$$$\Omega $$
  • $$8\ m$$$$\Omega $$
  • $$1\ m$$$$\Omega $$
A change of $$200\ mV$$ in base-emitter voltage causes a change of $$100\mu A$$ in the base current. The input resistance of the transistor is
  • $$2\ K$$$$\Omega $$
  • $$2$$ $$\Omega $$
  • $$2\ m$$$$\Omega $$
  • $$10\ K$$$$\Omega $$
In a common base circuit, if the collector base voltage is changed by $$0.6\ V$$, collector current changes by $$0.02\ mA$$. The output resistance will be
  • $$10^{4}\Omega $$
  • $$2\times 10^{4}\Omega $$
  • $$3\times 10^{4}\Omega $$
  • $$4\times 10^{4}\Omega $$
In a silicon transistor, a change of $$7.89\ mA$$ in the emitter current, produces a change of $$7.8\ mA$$ in the collector current. The change in the base current is necessary to produce an equivalent change in the collector current
  • $$90\ mA$$
  • $$90\ A$$
  • $$90\; \mu A $$
  • $$0.9\ mA$$
In a transistor circuit, the base current changes from $$30$$$$\mu A $$ to $$90$$$$\mu A$$. If the current gain of the transistor is $$30$$, the change in the collector current is
  • $$4\ mA$$
  • $$2\ mA$$
  • $$3.6\ mA$$
  • $$1.8\ mA$$
The minimum number of gates required to realise the expression $$Z = DABC + D\overline{ABC}$$ is
  • One
  • Two
  • Eight
  • Five
Logic gate having an output of $$1$$ is
Consider a two-input AND gate of figure below. Out of the four entries for the Truth Table given here, the correct ones are
16531.JPG
  • All
  • 1 and 2 only
  • 1, 2 and 3 only
  • 1, 3 and 4 only
Given above are four logic gate symbols. Those for OR, NOR and NAND are respectively
16552.jpg
  • a, d, c
  • d, a, b
  • a, c, d
  • d, b, a
From the adjacent circuit, the output voltage is

16496_c49a484e27ff43fca70f3349e69ed794.png
  • $$10 V$$
  • $$100 V$$
  • $$90 V$$
  • zero
The logic expression which is not equal to $$1$$ in Boolean algebra is
  • $$A+1$$
  • $$A . \bar{A}$$
  • $$A+\bar{A}$$
  • $$\overline{\overline {A+A}}$$
A Truth table is given below. The logic gate having following truth table is
A    B   Y
0    0    1
1    0    0
0    1    0
1     1    0
  • NAND gate
  • NOR gate
  • AND gate
  • OR gate
From the circuit shown below, the maximum and minimum value of zener diode current are :
16497_1a95c39592dd46d4b12a686fc3d73d3f.png
  • $$6\ mA,\ 5\ mA$$
  • $$14\ mA,\ 5\ mA$$
  • $$9\ mA,\ 1\ mA$$
  • $$3\ mA,\ 2\ mA$$
Boolean expression for the gate circuit shown below is
16559.png
  • $$A + \bar{A} =1$$
  • $$A+1=1$$
  • $$A+A=A$$
  • $$A+0=A$$
In the given circuit, two input wave forms $$A$$ and $$B$$ are applied simultaneously. The resultant wave form at $$Y$$ is
16563.png
The expression of $$Y$$ in the above circuit is
16576.png
  • $$ABCD$$
  • $$A+BCD$$
  • $$A +B+C+D$$
  • $$AB+CD$$
In the given circuit, if A and B represent two inputs and C represents the output, the circuit represents
16609.png
  • NOR gate
  • AND gate
  • gate
  • OR gate
The combinations of the NAND gates shown hereunder are equivalent to
16554.png
  • an OR gate and an AND gate respectively
  • an AND gate and a NOT gate respectively
  • an AND gate and OR gate respectively
  • an OR gate and an NOT gate respectively
The output $$Y$$ of the gate circuit shown in the figure below is 
16573.png
  • $$\overline{A.B}$$
  • $$\bar{A}.\bar{B}$$
  • $$\overline{\overline{A+B}}$$
  • $$\bar{A}+\bar{B}$$
The transistor are usually made of
  • metal oxides with high temperature coefficient of resistivity.
  • metals with high temperature coefficient of resistivity.
  • metals with low temperature coefficient of resistivity.
  • semiconducting materials having low temperature coefficient of resistivity.
To get an output $$1$$ from the circuit shown in the figure, the input must be 
16568.png
  • $$A=0, B=1,C=0$$
  • $$A=1, B=0, C=0$$
  • $$A=1, B=0, C=1$$
  • $$A=1, B=1, C=0$$
The arrangement shown in the figure performs the logic function of 
16566.png
  • AND gate
  • NAND gate
  • OR gate
  • XOR gate
The output of the combination of the gates shown in the figure is
16575.png
  • $$A + A. B$$
  • $$(A+B)A+\bar{B}$$
  • $$(A.B)+(\bar{A}.\bar{B})$$
  • $$(A+B)\overline{(A.B)}$$
Carbon, silicon and germanium have four valence electrons each. At room temperature the appropriate statement is
  • The number of free electrons for conduction is significant only in Si and Ge but small in C
  • The number of free conduction electrons is significant in C but small Si and Ge.
  • The number of free conduction electrons is negligibly small in all the three.
  • The number of free conduction electrons is significant in all the three.
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