CBSE Questions for Class 12 Medical Physics Semiconductor Electronics: Materials, Devices And Simple Circuits Quiz 1 - MCQExams.com

In a p-type semiconductor, the majority carries are
  • Electrons
  • Holes
  • -ve ions
  • +ve ions.
Logic gate realised from pn junctions shown in figure is
1268821_e4d3b631510c4ef7bc3bf95f3096163e.png
  • OR gate
  • AND gate
  • NOT gate
  • NOR gate
The principal of LASER action involves
  • amplification of particular frequency emitted by the system
  • population inversion
  • stimulated emission
  • All of the above
In common base circuit, output resistance is
  • very high
  • low
  • very low
  • moderate
For a transistor, $$\beta=100$$. The value of $$\alpha$$ is
  • $$1.01$$
  • $$0.99$$
  • $$100$$
  • $$0.01$$
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
What is the output Y in the following circuit when all the three inputs A, B, C are first $$0$$ and then $$1$$?

516334.png
  • $$1,1$$
  • $$0,1$$
  • $$0,0$$
  • $$1,0$$
The bond, that exists in a semiconductor is
  • covalent bond
  • ionic bond
  • metalic bond
  • hydrogen bond
In a transistor, 
  • length of emitter is greater than that of collector
  • length of collector is greater than that of emitter
  • both emitter and collector have same length
  • any one of emitter and collector can have greater length
Select the correct statement from the following:
  • A diode can be used as a rectifier
  • A triode cannot be used as a rectifier
  • The current in a diode is always proportional to the applied voltage
  • The linear portion of the I -V characteristic of a triode is used for amplification without distortion
An $$n-p-n$$ transistor has three leads $$A,\ B$$ and $$C$$. Connecting $$B$$ and $$C$$ by moist fingers, $$A$$ to the positive lead of an ammeter, and $$C$$ to the negative lead of the ammeter, one finds large deflection. Then, $$A,\ B$$ and $$C$$ refer respectively to :
  • Emitter, base and collector
  • Base, emitter and collector
  • Base, collector and emitter
  • Collector, emitter and base
In the given circuit the current through Zener Diode is close to : 
1332292_dda72ab576e441fb9ad3c3d4b5fd5570.PNG
  • $$6.0m\ A$$
  • $$4.0 m\ A$$
  • $$6.7\ mA$$
  • $$0.0\ mA$$
A working transistor with its three legs marked P, Q and R is tested using a multimeter. No conduction is found between P and Q. By connecting the common (negative) terminal of the multimeter to R and the other (positive) terminal to P or Q, some resistance is seen on the multimeter. 

Which of the following is true for the transistor?
  • It is a pnp transistor with R as emitter
  • It is an npn transistor with R as collector
  • It is an npn transistor with R as base
  • It is a pnp transistor with R as collector
The truth table given in figure represents:
474479.jpg
  • AND - Gate
  • NOR - Gate
  • NAND - Gate
  • OR - Gate
An experiment is performed to determine the $$I - V$$ characteristics of a Zener diode, which has a protective resistance of $$R = 100 \Omega$$, and a maximum power of dissipation rating of $$1 W$$. The minimum voltage range of the DC source in the circuit is
  • $$0-24 V$$
  • $$0-5 V$$
  • $$0-12 V$$
  • $$0-8 V$$

If a,b,c,d are inputs to a gate and x is its output then as per the following time graph the gate is:

472818.png
  • NOT
  • AND
  • OR
  • NAND
To get an output offrom the circuit shown in figure the input must be 

474870.JPG
  • $$a=0, b=0, c=1$$
  • $$a=1, b=0, c=0$$
  • $$a=1, b=0, c=1$$
  • $$a=0, b=1, c=0$$
Carbon, silicon and germanium have four valence electrons each. At room temperature which one ofthe following statements is most appropriate ?
  • The number of free conduction electrons is significant in C but small in Si and Ge
  • The number of free conduction electrons is negligibly small in all the three
  • The number of free electrons for conduction is significant in all the three
  • The number of free electrons for conduction is significant only in Si and Ge but small in C
Given : A and B are input terminals.
Logic $$1= > 5V$$
Logic $$0= < 1V$$
Which logic gate operation, the following circuit does?
100303.jpg
  • AND Gate
  • OR Gate
  • XOR Gate
  • NOR Gate
In an unbiased n-p junction electrons diffuse from n-region to p- region because
  • electrons travel across the junction due to potential difference.
  • electrons concentration in n region is more as compared to that in p-region.
  • holes in p-region attract them.
  • only electrons move from n- to p- region and not the vice-versa.
Two following figure shows a logic gate circuit with two inputs A and B and the output Y. The voltage wave forms of A, B and Y are as given.
The logic gate is

306008.png
  • NOR gate
  • OR gate
  • AND gate
  • NAND gate
For transistor action, which of the following statements is correct?
  • Base, emitter and collector regions should have same size.
  • Both emitter junction as well as the collector junction are forward biased
  • The base region must be very thin and lightly doped.
  • Base, emitter and collector regions should have same doping concentrations.
For transistor action, state which statements are true:
(1) Base, emitter and collector regions should have similar size and doping concentrations.
(2) The base  region must be very thin and lightly doped.
(3) The emitter-base junction is forward biased and base-collector junction is reverse biased
(4) Both the emitter-base junction as well as the base-collector junction are forward biased
  • (4) and (1)
  • (1) and (2)
  • (2) and (3)
  • (3) and (4)
The increase in the width of the depletion region in a p-n junction diode is due to :
  • reverse bias only
  • both forward bias and reverse bias
  • increase in forward current
  • forward bias only
The output (X) of the logic circuit shown in the figure will be

308365.png
  • $$X=\bar{\bar{A}}.\bar{\bar{B}}$$
  • $$X=\overline{A.B}$$
  • $$X=A.B$$
  • $$X=\overline{A+B}$$
In the given figure, a diode D is connected to an external resistance $$R = 100\;\Omega$$ and an $$e.m.f.$$ of $$3.5\ V$$. If the barrier potential developed across the diode is $$0.5\ V$$, the current in the circuit will be 
420847.png
  • $$35\ mA$$
  • $$30\ mA$$
  • $$40\ mA$$
  • $$20\ mA$$
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
306837.png
  • $$10\ mA$$
  • $$15\ mA$$
  • $$20\ mA$$
  • $$5\ mA$$
When the input of a two input logic gate are 0 and 0, the output isWhen the inputs are 1 and 0, the output is zero. The type of logic gate is
  • XOR
  • NAND
  • NOR
  • OR
The logic gate represented in given figure is
468086.PNG
  • OR Gate
  • NOT Gate
  • NAND Gate
  • XOR Gate
In the given circuit, the voltage across the voltage across the load is maintained at 12V. The current in the zener diode varies from 0-50 mA. What is the maximum watage of the diode?

469172.jpg
  • 12 W
  • 6 W
  • 0.6 W
  • 1.2 W
The circuit as shown in figure, the equivalent gate is

469127.png
  • NOR gate
  • OR gate
  • AND gate
  • NAND gate
p-n junction diode acts as
  • ohmic resistance
  • non-ohmic resistance
  • both A and B
  • amplifier
Which of the following contains a covalent bond?
  • $$copper$$
  • $$NaCl$$
  • $$germanium$$
  • $$helium$$
The main cause of avalanche breakdown is
  • ionisation by collision.
  • high doping.
  • recombination of electrons and holes.
  • low doping.
The main cause of Zener breakdown is
  • the base semiconductor being germanium.
  • production of electron-hole pairs due to thermal excitation.
  • low doping.
  • high doping.
The process of converting alternating current into direct current is known as
  • modulation
  • amplification
  • detection
  • rectification
In an intrinsic semiconductor, conductivity is
  • low at room temperature
  • average
  • high at room temperature
  • zero at room temperature
The value indicated by Fermi energy level in an intrinsic semiconductor is
  • the average energy of electrons and holes.
  • the energy of electrons in conduction band.
  • the energy of holes in valence band.
  • the energy of forbidden region.
In an intrinsic semiconductor, the Fermi energy level is
  • nearer to valence band than conduction band.
  • equidistant from conduction band and valence band.
  • nearer to conduction band than valence band.
  • bisecting the conduction band.
In an intrinsic semiconductor, conductivity is due to
  • doping
  • breaking of covalent bonds
  • free electrons
  • holes
p-n junction diode can be used as
  • amplifer
  • detector
  • oscillator
  • capacitor
When the conductivity of a semiconductor is only due to breaking of covalent bonds, the semiconductor is called
  • n-type
  • p-type
  • intrinsic
  • extrinsic
In a junction transistor the emitter, base and collector are made of
  • extrinsic semiconductors.
  • intrinsic semiconductors.
  • both A and B.
  • metal.
The avalanche breakdown in p-n junction is due to
  • shift of Fermi level.
  • cumulative effect of conduction band electron.
  • widening of forbidden gap.
  • high impurity concentration.
The current flow in a Zener diode is mainly due to
  • thermally generated charge carriers
  • minority charge carriers
  • collision generated charge carriers
  • ions
A Zener diode
  • is a lightly doped junction diode.
  • heavily doped junction diode.
  • is either p-type or n-type.
  • has no p-n junction.
If ‘p’ region of a semi conductor is connected to negative and ‘n’ region to positive pole, it is said to be
  • directed biased
  • unbiased
  • forward biased
  • reverse biased
In a transistor,
  • both emitter and the collector are equally doped
  • base is more heavily doped than collector
  • collector is more heavily doped than the emitter
  • the base is made very thin and is lightly doped
Among the following which one gives output $$1$$ in the AND gate.
  • $$A = 0,\ B = 0$$
  • $$A = 1,\ B = 1$$
  • $$A = 1,\ B = 0$$
  • $$A = 0,\ B = 1$$
In a common -base amplifier, the phase difference between the input signal voltage and output voltage is : 
  • $$\dfrac{\pi }{4}$$
  • $$\pi$$
  • $$0$$
  • $$\dfrac{\pi }{2}$$
0:0:1


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