CBSE Questions for Class 12 Medical Physics Semiconductor Electronics: Materials, Devices And Simple Circuits Quiz 2 - MCQExams.com

In a $$p-n-p$$ transistor the base is the n-region. Its width relative to the p-regions is
  • smaller
  • larger
  • same
  • not related
In positive logic, the logic state $$1$$ corresponds to
  • positive voltage
  • zero voltage
  • lower voltage level
  • higher voltage level
In Boolean algebra, $$A + B = Y$$ implies that 
  • sum of $$A$$ and $$B$$ is $$Y$$.
  • $$Y$$ exists when $$A$$ exists or $$B$$ exists or both $$A$$ and $$B$$ exist.
  • $$Y$$ exists only when $$A$$ and $$B$$ both exist.
  • $$Y$$ exists when $$A$$ or $$B$$ exist but not when both $$A$$ and $$B$$ exist.
In a transistor the base is made very thin and is lightly doped with an impurity, because
  • to enable the collector to collect about $$95\%$$ of the holes or electrons coming from the emitter side
  • to enable the emitter to emit small number of holes or electrons
  • to save the transistors from high current effects
  • to enable the base to collect about $$95\%$$ of holes or electrons coming from the emitter side
A p-n-p transistor is said to be in active region of operation when
  • both emitter junction and collector junction are forward biased.
  • both emitter junction and collector junction are reverse biased.
  • emitter junction is forward biased and collector junction is reverse biased.
  • emitter junction is reverse biased and collector junction is forward biased.
The part of a trasistor which is heavily doped to produce large number of majority carriers is :
  • emitter
  • base
  • collector
  • can be any of the above three
Which of the following is not the function of a NOT gate?
  • Stop a signal.
  • Invert an input signal.
  • Complement a signal.
  • Change the logic in a digital circuit.
When an input signal $$1$$ is applied to a NOT gate, its output is
  • $$1$$
  • $$0$$
  • either $$0$$ or $$1$$
  • both $$0$$ and $$1$$
The symbol represents

16081.png
  • NOT gate
  • OR gate
  • AND gate
  • NOR gate
A transistor has a base current of $$1\ mA$$ and emitter current $$100\ mA$$. The current transfer ratio will be
  • $$0.9$$
  • $$0.99$$
  • $$1.1$$
  • $$10.1$$
An AND gate is followed by a NOT gate in series. With two inputs $$A$$ & $$B$$, the Boolean expression for the out put $$Y$$ will be :
  • $$A.B$$
  • $$A + B$$
  • $$\overline{A+B}$$
  • $$\overline{A.B}$$
The gate that has only one input terminal
  • NOT
  • NOR
  • NAN
  • XOR
In Boolean algebra $$A.B = Y$$ implies that :
  • product of $$A$$ and $$B$$ is $$Y$$
  • $$Y$$ exists when $$A$$ exists or $$B$$ exists
  • $$Y$$ exists when both $$A$$ and $$B$$ exist but not when only $$A$$ or $$B$$ exists
  • $$Y$$ exists when $$A$$ or $$B$$ exists but not both $$A$$ and $$B$$ exist.
In the Boolean algebra, the following one is wrong
  • $$1 + 0 = 1$$
  • $$0 + 1 = 1$$
  • $$1 + 1 = 1$$
  • $$0 + 0 = 1$$
The output of a 2-input OR gate is zero only when its
  • both inputs are $$0$$.
  • either input is $$1$$.
  • both inputs are $$1$$.
  • either input is $$0$$.
NOR gate is the series combination of
  • NOT gate followed by OR gate.
  • OR gate followed by NOT gate.
  • AND gate followed by OR gate.
  • OR gate followed by AND gate.
The following truth table is for :
ABY
110
101
011
001
  • NAND gate
  • AND gate
  • XOR gate
  • NOT gate
If $$A = B = 1$$, then in terms of Boolean algebra the value of $$A.B + A$$ is not equal to
  • $$B.A+B$$
  • $$B+A$$
  • $$B$$
  • $$\bar{A}.B$$
In the Boolean algebra, of the following one which is not equal to $$A$$ is
  • $$A.A$$
  • $$A + A$$
  • $$\bar{A}.A$$
  • $$\overline{\bar A + \bar A}$$
In the Boolean algebra : $$A + B =$$
  • $$\bar{A}$$+$$\bar{B}$$
  • A.B
  • $$\bar{\bar{A}}+\bar{\bar{B}}$$
  • $$\bar{\bar{A}}$$+$$\bar{B}$$
A change of $$400\ mV$$ in base-emitter voltage causes a change of $$200$$$$\mu A $$ in the base current. The input resistance of the transistor is
  • $$1K$$$$\Omega $$
  • $$6K$$$$\Omega $$
  • $$2K$$$$\Omega $$
  • $$8K$$$$\Omega $$
For a p-n-p transistor in CB configuration, the emitter current $$I_{E}$$ is $$1\ mA$$ and $$\alpha $$ $$=$$$$0.95$$. The base current and collector current are
  • $$0.95\ mA, 0.05\ mA$$
  • $$0.05\ mA , 0.95\ mA$$
  • $$9.5\ mA, 0.5\ mA$$
  • $$0.5\ mA, 9.5\ mA$$
If $$A = 1$$ and $$B = 0$$, then in terms of Boolean algebra the value of $$A.A + B$$ is
  • $$A$$
  • $$B^2$$
  • $$B$$
  • $$A \cdot B$$
If $$A = 1, B = 0$$ then the value of $$\bar {A} + B $$ in terms of Boolean algebra is
  • $$A$$
  • $$B$$
  • $$B + A$$
  • $$A.\bar{B}$$
The following one represents logic addition is 
  • $$1 + 1 = 2$$
  • $$1 + 1 = 10$$
  • $$1 + 1 = 1$$
  • $$1 + 1 = 11$$
The value of $$\alpha $$ of a transistor is $$0.9$$. The change in the collector current corresponding to a change of $$4\ mA$$ in the base current in a common emitter arrangement is
  • $$36\ mA$$
  • $$72\ mA$$
  • $$18\ mA$$
  • $$54\ mA$$
In the Boolean algebra :  $$\bar{A} . \bar{B}=$$ ......
  • $$\overline{A+B}$$
  • $$A.B$$
  • $$\overline{\bar A + \bar B}$$
  • $$A + B$$
The output of OR gate is 1 :-
  • If either one or both inputs are 1
  • Only if both inputs are 1
  • If either input is zero
  • If both inputs are zero
Identify the logic gate in figure.

16549.png
  • NAND
  • NOR
  • NOT
  • AND
The truth table for NOT gate is
The logic expression which is NOT true in Boolean algebra is
  • $$[\bar{1}+\bar{1}].1=0$$
  • $$[\bar{1}+0].1=0$$
  • $$[\bar{1}+0].\bar{1}=0$$
  • $$[1+1].1=0$$
Which one of the following statement is false 
  • Work is a state finction
  • temperature is a state function
  • Change in the state is completely defined when the initial and final states are specified
  • Work appears at the boundary of the system
The device that can act as a complete electronic circuit is -
  • Junction diode
  • Integrated circuit
  • Junction transistor
  • Zener diode
Boolean Expression for the gate circuit shown in the figure is
16562.png
  • $$A. 1 = A$$
  • $$A.\bar{A}=0$$ 
  • $$A.A = A$$
  • $$A.0 = 0$$
NAND gate in the following is
The logic gate having following truth table is
A   B   Y
0    0   1
0    1    1
1    0    1
1    1    0 
  • XOR
  • OR
  • AND
  • NAND
Why are LEDs extensively used to replace bulbs? 
85010.png
  • (i) and (ii) only
  • (ii) and (iii) only
  • (iii) and (i) only
  • (i), (ii) and (iii)
Semiconductors are generally made up of which substance?
  • Silicon
  • Carbon
  • Phosphorus
  • Boron
The device which produces highly coherent sources is 
  • Fresnel bi-prism
  • Young's double slit
  • LASER
  • Lloyd's mirror
In an intrinsic semiconductor, the number of electrons in the conduction band is ________ the number of holes in the valence band.
  • equal to
  • less than
  • greater than
  • none of these
Given figure is the symbol, for which component of a circuit?
591582.png
  • LED
  • Rheostat
  • Transistor
  • Resistor
Which are good conductors ?
  • silicon
  • Silver
  • copper
  • glass
The energy gap in glass at room temperature is
  • Greater than that in a semiconductor.
  • Less than that in a good conductor.
  • Greater than that in a good conductor.
  • Both (1) and (3) are true.
Materials which allow only larger currents to flow through them are
  • Insulators
  • Semi-conductors
  • Conductors
  • Alloys
In an intrinsic semiconductor, if $$N_e$$ is the number of electrons in the conduction band and $$N_p$$ is the number of holes in the valence band then.
  • $$N_e > N_p$$
  • $$N_e = N_p$$
  • $$N_e < N_p$$
  • None of the above
The Wavelength of a LASER beam can be used as a standard of 
  • time
  • temperature
  • angle
  • length
A pure semiconductor at absolute zero has
  • Absence of electrons in the conduction band.
  • All the electrons occupying the valence band.
  • Large $$E_g$$ value.
  • All of the above.
In n-type of semiconductor, majority carries are
  • Positron
  • Electron
  • Holes
  • Impure particles
In a transistor, the base is
  • a conductor of low resistance
  • a conductor of high resistance
  • an insulator
  • an extrinsic semiconductor
A transistor has a base current of $$1\ mA$$ and emitter current $$90\ mA$$. The collector current will be
  • $$90\ mA$$
  • $$1\ mA$$
  • $$89\ mA$$
  • $$91\ mA$$
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