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JEE Questions for Physics Semiconductor Devices Quiz 3 - MCQExams.com
JEE
Physics
Semiconductor Devices
Quiz 3
A valanche breakdown in a
p-n
junction diode is due to
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sudden shift of Fermi level
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increase in the width of forbidden gap
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sudden increase of impurity concentration
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cumulative effect of increased electron collision and creation of added electron-hole pairs
An electron-hole pair is formed when light of maximum wavelength 6000 Å is incident on the semiconductor. What is the bond gap energy of the semiconductor? (
h
= 6.62 × 10
-34
J-s )
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3.31 × 10-19 J
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3.07 × 10-19 J
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2.07 × 10-19 J
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2.07 J
In the following circuit, the current flowing through 1 kΩ resistor is
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zero
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5 mA
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10 mA
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15 mA
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20 mA
For a common emitter amplifier, the audio signal voltage across the collector resistance 2 kΩ is 2V. If the current amplification factor of the transistor is 220, and the base resistance is 1.5Ω, the input signal voltage and base current are
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0.1 V and 1µA
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0.15 V and 10µA
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1.015 V and 1 A
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0.0015 V and 1 mA
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0.0075 V and 5µA
The graph given below represents the
I-V
characteristics of a zener diode. Which part of the characteristics curve is most relevant for its operation as a voltage regulator?
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ab
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bc
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cd
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de
The reverse saturation of
p-n
diode
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depends on doping concentrations
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depends on diffusion lengths of carriers
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depends on the doping concentrations and diffusion lengths
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depends on the doping concentrations, diffusion length and device temperature
In semiconductors at a room temperature,
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the valence band is partially empty and the conduction band is partially filled
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the valence band is completely filled and tile conduction band is partially filled
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the valence band is completely filled
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the conduction band is completely empty
A
p-n
photodiode is made of a material with a band gap of 2.0 eV, The minimum frequency of the radiation that can be absorbed by the material is nearly
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10 × 1014 Hz
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5 × 1014 Hz
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1 × 1014 Hz
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20 × 1014 Hz
A reverse biased diode is
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0%
2)
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In an unbiased
p-n
junction
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potential at p is more than that at n
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potential at p is less than that at n
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potential at p is equal to that at n
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potential at p is +ve and that at n is -ve
The current
I
through 10 Ω resistor in the circuit given below is
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50 mA
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20 mA
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40 mA
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80 mA
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35 mA
A Si and Ge diode has identical physical dimensions. The band gap in Si is larger than that in Ge. An identical reverse bias is applied across the diodes
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the reverse current in Ge is larger than that in Si
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the reverse current in Si is larger than that in Ge
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the reverse current is identical in the two diodes
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the relative magnitude of the reverse currents cannot be determined from the given data only
The charge carriers in a
p
-type semiconductor are
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electrons only
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holes only
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holes in larger numbers and electrons in smaller numbers
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holes and electrons in equal numbers
The electrical conductivity of an intrinsic semiconductor at 0 K is
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less than that of an insulator
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is equal to zero
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is equal to infinity
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more than that of an insulator
If
n
E
and
n
H
represent the number of free electrons and holes respectively in a semiconducting material, then for
n
- type semiconducting material
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nE << nH
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nE >> nH
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nE = nH
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nE = nH = 0
An intrinsic semiconductor at 0 K temperature behaves like
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conductor
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p -type semiconductor
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n-type semiconductor
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insulator
When a
p -n
junction diode is connected in forward bias its barrier potential
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decreases and less current flows in the circuit
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decreases and more current flows in the circuit
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increases and more current flows in the circuit
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decreases and no current flows in the circuit
The main cause of zener breakdown is
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the base semiconductor being germanium
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production of electron-hole pairs due to thermal excitation
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low doping
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high doping
The depletion layer in a silicon diode is 1 μm wide and its knee potential is 0.6 V, then the electric field in the depletion, layer will be
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0.6 Vm-1
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6 × 104 Vm-1
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6 × 104 Vm-1
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zero
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
R
is
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40 kΩ
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4 kΩ
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200 kΩ
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400 Ω
When a
p-n
junction diode is reverse biased, then
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no current flows
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the depletion region is increased
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the depletion region is reduced
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the height of the potential barrier is reduced
To a germanium crystal equal number of aluminium and indium atoms are added. Then
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it remains an intrinsic semiconductor
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it becomes a n-type semiconductor
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it becomes a p-type semiconductor
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it becomes an insulator
If in a
p-n
junction diode, a square input signal of 10 V is applied as shown in the figure
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2)
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A conductor and a semiconductor are connected in parallel as shown in the figure. At a certain voltage both ammeters register the same current. If the voltage of the DC source is increased then the
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ammeter connected to the semiconductor will register higher current than the ammeter connected to the conductor
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ammeter connected to the conductor will register higher current than the ammeter connected to the semiconductor
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ammeters connected to both semiconductor and conductor will register the same current
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ammeters connected to both semiconductor and conductor will register no change in the current
Minority carriers in a
p
-type semiconductor are
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free electrons
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holes
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Neither holes nor free electrons
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Both holes and free electrons
The difference in the variation of resistance with temperature in a metal and a semiconductor arises essentially due to the difference in the
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crystal structure
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variation of the number of charge carriers with temperature
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type of bonding
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variation of scattering mechanism with temperature
In the middle of the depletion layer of reverse biased
p-n
junction, the
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electric field is zero
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potential is maximum
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electric field is maximum
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potential is zero
In a reverse biased diode when the applied voltage changes by 1 V, the current is found to change by 0.5 μA. The reverse bias resistance of the diode is
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2 × 105 Ω
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2 × 106 Ω
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200 Ω
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2 Ω
A photodetector used to detect the wavelength of 1700 nm, has energy gap of about
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0.073 eV
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1.2 eV
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7.3 eV
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1.16 eV
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0.73 eV
The energy gap between conduction band and the valence band is of the order of 0.7 eV. Then it is
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an insulator
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a conductor
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a semiconductor
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an alloy
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a superconductor
The depletion layer of a
p-n
junction
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is of constant width irrespective of the bias
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acts like an insulating zone under reverse bias
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has a width that increases with an increase in forward bias
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is depleted of ions
The current in the circuit shown in the figure, considering ideal diode is
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20 A
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2 × 10-3 A
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200 A
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2 × 10-4 A
In depletion layer of unbiased
p-n
junction
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holes are present
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electrons are present
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only fixed ions are present
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None of the above
Why is there sudden increase in current in zener diode ?
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Due to rupture of bonds
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Resistance of depletion layer becomes less
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Due to high doping
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None of the above
In an
n
-type semiconductor, the fermi energy level lies
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in the forbidden energy gap nearer to the conduction band
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in the forbidden energy gap nearer to the valence band
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in the middle of forbidden energy gap
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outside the forbidden energy gap
The temperature of germanium is decreased from room temperature to 100 K, the resistance of germanium
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decreases
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increases
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unaffected
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depends on external conditions
The diode used in the circuit shown in the figure, has a constant voltage drop of 0.5 V at all currents and a maximum power rating of 100 milli-watt. What should be the value of the resistance
R
, connected in series with the diode, for obtaining maximum current ?
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1.5 Ω
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5 Ω
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6.67 Ω
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200 Ω
When
n-p-n
transistor is used as an amplifier
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electrons move from base to collector
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holes move from emitter to base
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electrons move from collector to base
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holes move from base to emitter
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2)
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The circuit has two oppositely connected ideal diodes in parallel. What is the current flowing in the circuit ?
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1.71 A
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2.00 A
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2.31 A
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1.33 A
In the following, which one of the diodes is reverse biased ?
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2)
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Doping of intrinsic semiconductor is done
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to neutralise charge carriers
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to increase the concentration of majority charge carriers
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to make it neutral before disposal
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to carry out further purification
On increasing the reverse bias to a large value in a
p-n
junction, diode current
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increases slowly
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remains fixed
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suddenly increases
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decreases slowly
With in depletion region of
p-n
junction diode
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p-side is positive and n-side is negative
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p-side is negative and n-side is positive
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Both sides are positive or both negative
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Both side are neutral
In a forward biased
p-n
junction diode, the potential barrier in the depletion region is of the form
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2)
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Application of a forward bias to a
p-n
junction
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increases the number or donors on the n -side
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increases the electric field in the depletion zone
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increases the potential difference across (the depletion zone)
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widens the depletion zone
The electrical conductivity of a semiconductor increases when electromagnetic radiation of wavelength shorter than 2480 nm, is incident on it, The band gap in (eV) for the semiconductor is
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1.1 eV
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2.5 eV
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0.5 eV
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0.7 eV
Frequency of given AC signal is 50 Hz. When it is connected to a half-wave rectifier, the number of output pulses given by rectifier within 1 s is
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50
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100
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25
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150
Identify the property which is not characteristic for a semiconductor ?
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At a very low temperature, it behaves like an insulator
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At higher temperatures two types of charge carriers will cause conductivity
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The charge carriers are electrons and holes in the valence band at higher temperatures
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The semiconductor is electrically neutral
In a
p-n
junction diode acting as a half-wave rectifier, which of the following statement is not true ?
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the average output voltage over a cycle is non-zero
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The drift current depends on biasing
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The depletion zone decreases in forward biasing
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The diffusion current increases due to forward biasing
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