CBSE Questions for Class 12 Medical Physics Semiconductor Electronics: Materials, Devices And Simple Circuits Quiz 7 - MCQExams.com

In a n-p-n transistor
  • holes move from emitter to base
  • holes move from base to collector
  • negative charge moves from emitter to base
  • negative charge moves from collector to base

LED glows even when a ______ electric current passes through it. Fill in the blank.
  • weak
  • strong 
  • can't predicted  
  • none of the  above 
Choose the wrong statement regarding the experiment to identify a diode, and LED, a resistor and a capacitor
  • when pointer moves in one way when voltage is applied and doesn't move when reversed and there is light emission, the item is LED
  • when pointer moves in one way when voltage is applied and doesn't move when reversed and there is no emmision of light, the item is a diode
  • when pointer moves in one way when voltage is applied and not when reversed, the item is a resistor
  • None of these
Calculate the plate resistance r$$_p$$ of the triode valve?
  • $$0.12$$ $$\times$$ $$10$$$$^4$$ ohm
  • $$1.2$$ $$\times$$$$ 10$$$$^4$$ ohm
  • $$1.3$$ $$\times$$ $$10$$$$^4$$ ohm
  • $$1.4$$ $$\times$$ $$10$$$$^4$$ ohm
State whether true or false : 
A bulb is used in place of LED to detect weak currents.
  • True
  • False
Which one of the following statements is not correct of for a junction transistor?
  • The base region is very thin.
  • Emitter is more heavily doped as compared to collector.
  • Emitter and collector can be interchanged.
  • The surface area of collector is quite large as compared to emitter.
Diodes are used to ___________.
  • convert DC into AC
  • convert AC into DC
  • resistance control
  • current regulation
The device used for converting alternating current to direct current is called
  • Rectifier
  • Induction coil
  • Transmitter
  • Transformer
Transistor act as a 
  • Conductor
  • Semi-conductor
  • Insulator
  • Thermionic valve
The most widely used semiconductors are
(i) silicon  (ii) germanium
(iii) phosphorus   (iv) arsenic
  • (i) and (ii)
  • (ii) and (iii)
  • (iii) and (iv)
  • (i), (ii), (iv),(iii)
Which logic gate is represented by following diagram?
347603.png
  • XOR
  • NOR
  • OR
  • AND
A moving coil galvanometer is converted into an ammeter by putting
  • A high resistance in parallel
  • A low resistance in series
  • A low resistance in parallel
  • A high resistance in series
The conductivity of a magnetic substance for the lines of force with respect to air is called the
  • Magnetic induction
  • Magnetic permeability
  • Magnetic flux density
  • Intensity of magnetisation
In a $$p$$-type semi-conductor, the majority carriers are
  • Protons
  • Electrons
  • Holes
  • Positive ions
An electrical device which offers a low resistance to the current in one direction but a high resistance to the current in opposite direction is:
  • Current Amplifier
  • Oscillator
  • Power Amplifier
  • Rectifier
The primary source of holes in $$p-n-p$$ transistors is the:
  • Transmitter
  • Collector
  • Base
  • Emitter
Different voltage are applied across a p-n junction and the currents are measured for each value. Which of the following graphs is obtained between voltage V and current i:
When an intrinsic semiconductor is connected to an electric cell, the holes move towards the _________ terminal of the cell.
  • Holes, negative positive
  • Electron, negative
  • Electrons, positive
  • Both (1) and (3)
The width of the depleted region of a p-n junction is of the order of a few tenth of a ________.
  • millimeter
  • micrometer
  • metre
  • nanometre
n-type silicon is obtained by:
  • doping with tetravalent element
  • doping with pentavalent element
  • doping with trivalent element
  • doping with a mixture of trivalent and tetravalent current
Transistors are not used in
  • amplifier circuits
  • oscillators
  • switching circuits
  • voltage regulation
Which of the following doping will produce a p-type semiconductor?
  • Germanium with phosphorus
  • Silicon with germanium
  • Germanium with antomony
  • Silicon with indium
The following circuit acts as a __________ .
393775_1723087656a248e6b775cf099429c520.png
  • half wave rectifier
  • amplifier
  • full wave rectifier
  • oscillator
p-n junction is said to be forward bias. If
  • the n-side is connected to the -ve side and p-side to the +ve terminal of an external battery.
  • the n-side is connected to the +ve side and p-side to the -ve side of an external battery.
  • n-side is connected to +ve terminal and p-side in neutral.
  • none of these
Space charge region around a p-n junction:
  • does not contain mobile carriers
  • contains both free electrons and holes
  • contains one type of mobile carriers depending on the level of doping
  • contains electrons only as free carriers
For transistor action, which of the following statements are correct:
  • Base, emitter and collector regions should have similar size and doping concentrations
  • The base region must be very thin and lightly doped
  • The emitter junction is forward biased and collector junction is reverse biased
  • Both the emitter junction as well as the collector junction are forward biased
Which logic gates is represented by the following combination of logic gates?
432577.png
  • OR
  • NAND
  • AND
  • NOR
The transfer ratio $$\beta$$ of a transistor is $$50$$. The input resistance of the transistor, when used in the common emitter configuration is $$1k\Omega$$. The peak value of the collector A.C current for an A.C input voltage of $$0.01V$$, is :
  • $$500\mu A$$
  • $$0.25\mu A$$
  • $$0.01\mu A$$
  • $$100\mu A$$
When the two semiconductor p- and n- type are brought into contact they form a p-n junction, which acts like a/an:
  • rectifier
  • amplifier
  • conductor
  • oscillator
Diode is used as a/an
  • moculator
  • rectifier
  • oscillator
  • amplifier
The value of current gain $$\alpha$$ of a transistor is $$0.98$$. The value of $$\beta$$ will be
  • $$490$$
  • $$4.9$$
  • $$59$$
  • $$49$$
In n-p-n transistor circuit the collector current is $$10mA$$. If $$90\%$$ of the electron reach the collector, then emitter current will be
  • $$1mA$$
  • $$0.1mA$$
  • $$2mA$$
  • nearly $$11mA$$
The circuit given represents which of logic operations
432589.png
  • AND
  • NOT
  • OR
  • NOR
The delpetion layer in a p-n junction diode is $$10^{-6}m$$ wide and its knee potential is $$0.5V$$, then the inner electric field in the depletion region is:
  • $$5\times 10^{6}V/m$$
  • $$5\times 10^{-7}V/m$$
  • $$5\times 10^{5}V/m$$
  • $$5\times 10^{-1}V/m$$
Identify the logic operation of the following logic circuit:
432618.png
  • NAND
  • AND
  • NOR
  • OR
As we are growing in technology, use of wires in an electrical circuit is reducing. This is done by using semiconductor chips or reducing length of wire as much as possible. What could be the possible reason for the above? 
  • Using chips allows more compact devices
  • Heat loss in wires is reduced
  • Power requirements are reduced
  • All of the above
The part of a transistor which is heavily dopped to produce a large number of majority carriers is:
  • Base
  • Emitter
  • Collector
  • None of these
A solid reflects incident light and its electrical conductivity decreases with temperature. The bonding in this solid is :
  • ionic
  • covalent
  • metallic
  • molecular
Consider an n-p-n transistor amplifier in common emitter configuration. The current gain of the transistor is $$100$$. If the collector current changes by $$1mA$$, what will be the change in emitter current
  • $$1.1mA$$
  • $$1.01mA$$
  • $$0.01mA$$
  • $$10mA$$
The follwoing combined logic gate diagram is eqivalent to
468964.jpg
  • NOR gate
  • OR gate
  • AND gate
  • NAND gate
In a $$p-n$$ junction photocell, the value of photoelectromotive force produced by monochromatic light is proportional to
  • The voltage applied at $$p-n$$ junction
  • The barrier voltage at $$p-n$$ junction
  • The intensity of light falling on cell
  • The frequency of light falling on cell
Which logic gate is represented by the following combination of logic gates?
467237.png
  • OR
  • NOR
  • AND
  • NAND
Which type of gate the following truth table represents?
InputInputOutput
$$A$$$$B$$$$Q$$
$$0$$$$0$$$$1$$
$$0$$$$1$$$$1$$
$$1$$$$0$$$$1$$
$$1$$$$1$$$$0$$
  • NOT
  • AND
  • OR
  • NAND
In the following circuit the output Y becomes zero for the input combinations:
475030_20a682de7aa543b4bd725ca2b1bed15a.png
  • A=1, B=0, C=0
  • A=0, B=1, C=1
  • A=0, B=0, C=0
  • A=1, B=1, C=0
The truth tables of logic gates A, B, C, D are given here. Identify them correctly.
475028.jpg
  • A:  OR, B:  AND, C:  NOR, D:  NAND
  • A:  OR, B:  NOR, C:  AND, D:  NAND
  • A:  AND, B:  OR, C:  NAND, D:  NOR
  • A:  OR, B:  NOR, C:  NAND, D:  AND
Of the following NAND gate is :
Students in a lab are trying to determine the wavelength of laser light by shining the laser through two narrow slits separated by $$9.60$$ micrometers toward a screen $$4.00$$ meters away. The first order bright fringes are $$23.0$$ centimeters from the center fringe.
What wavelength do the students determine?
  • $$680 nm$$
  • $$552 nm$$
  • $$883 nm$$
  • $$167 nm$$
  • $$8,832 nm$$
The rating of a zener diode is $$1 W, 15 V$$. Find the zener maximum current. 
  • $$66.7 A$$
  • $$1 A$$
  • $$15 A$$
  • $$66.7 mA$$
Which of the following logic expressions represents the logic diagram shown ?
508057_8e666fd83a704d5bacf95f339ed97241.png
  • $$X = A\overline B + \overline A B$$
  • $$X = \overline {AB} + A B$$
  • $$X = \overline {AB} + \overline A \overline B$$
  • $$X = \overline A\overline B + A B$$

Find the maximum zener current for the zener diode as shown in figure. Given, $$V_Z=6 V, R_Z=1.5 \Omega,  R=400 \Omega $$
507051_a10e5151f11045c6981e20efade10678.png
  • $$35.00 mA$$
  • $$30.87 mA$$
  • $$34.87 mA$$
  • $$34.87 A$$
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