CBSE Questions for Class 12 Medical Physics Semiconductor Electronics: Materials, Devices And Simple Circuits Quiz 13 - MCQExams.com

In the given circuit, diode $$D$$ is ideal. The potential difference across $$4\Omega$$ resistance is:
1704675_b0ffbd494c6b4001a5a11728a9d9e36c.png
  • $$10\ V$$
  • $$5\ V$$
  • $$4\ V$$
  • $$none\ of\ these$$
What is the plate current in a diode valve under the space charge limited operation, when the plate potential is $$60\ V$$? In a diode valve, the plate current is $$320\ mA$$, when the plate potential is $$240$$ volts:
  • $$30\ mA$$
  • $$20\ mA$$
  • $$40\ mA$$
  • $$10\ mA$$
In the given diagram, assume that diode is not ideal. The drift current for diode is $$40\mu A$$. The potential difference across the $$4\Omega$$ resistance is:
1704682_6fed59a38924467983fc8c36bced9755.png
  • $$10\ V$$
  • $$40\times 10^{-6}V$$
  • $$160\times 10^{-6}\ V$$
  • $$none\ of\ these$$
Choose the correct option for the forward biased characteristics of a $$p-n$$ junction:
What is the work function of tungsten at $$1500\ K$$ temperature, when a diode valve with a tungsten filament works at $$1500\ K$$? Assume the work function of tungsten at $$0\ K$$ is $$4.52\ eV$$:
  • $$4.71\ eV$$
  • $$0.39\ eV$$
  • $$8.86\ eV$$
  • $$1.25\ eV$$
If both the collector  and emitter junctions of a transistor are forward biased, the transistor is said to operate in the:
  • active region
  • saturation region
  • cut off region
  • none of these
In a $$p-n$$ junction diode, holes diffuse from the $$p-$$ region to the $$n-$$ region because:
  • the free electrons in the $$n-$$ region attract them
  • the are swept across the junction by the potential difference
  • there is greater concentration of holes in the $$p-$$ region as compared to $$n-$$ region
  • none of the above
A transistor operating in a common base configuration has forward current gain factor, $$\alpha=0.99$$. If the emitter current changes by $$1\ mA$$, then the changes in teh base current will be:
  • $$100\ mA$$
  • $$0.01\ mA$$
  • $$0.99\ mA$$
  • $$99\ mA$$
In case of $$p-n$$ junction diode at high value of reverse bias, current rises sharply. The value of reverse bias is called:
  • cut off voltage
  • inverse voltage
  • zener voltage
  • critical voltage
The energy gap between conduction band and valence band is of the order of $$0.07\ eV$$. It is a:
  • insulator
  • conductor
  • semiconductor
  • alloy
In the active region operation of a transistor:
  • the collector-emitter junction is forward biased
  • the collector-emitter junction is reverse biased
  • the collector-base junction is forward biased and the emitter junction is reverse biased
  • the collector junction is reverse biased and emitter-base junction is forward biased
Mark the correct options. 
  • A diode valve can be used as a rectifier.
  • A triode valve can be used as a rectifier.
  • A diode valve can be used as an amplifier.
  • A triode valve can be used as an amplifier.
The anode of a thermionic diode is connected to the negative terminal of a battery and the cathode to its positive terminal.
  • No appreciable current will pass through the diode.
  • A large current will pass through the diode from the anode to the cathode.
  • A large current will pass through the diode from the cathode to the anode.
  • The diode will be damaged.
The saturation current in a triode valve can be changed by changing 
  • the grid voltage
  • the plate voltage
  • the separation between the grid and the cathode
  • the temperature of the cathode.
A triode is operated in the linear region of its characteristics. If the plate voltage is slightly increased, the dynamic plate resistance will 
  • increase
  • decrease
  • remain almost the same
  • become zero.
The plate current in a triode valve is maximum when the potential of the grid is
  • positive
  • zero
  • negative
  • nonpositive
In a p-n junction with open ends,
  • there is no systematic motion of charge carriers
  • holes and conduction electrons systematically go from the p-side to the n-side and from the n-side to the p-side respectively
  • doping donor impurities
  • irradiating ultraviolet light on it.
Because of the space charge in a diode valve, 
  • the plate current decreases
  • the plate voltage increases
  • the rate of emission of thermions increases
  • the saturation current increases.
When the diode shows saturated current, dynamic plate resistance is
  • zero
  • infinity
  • indeterminate
  • different for different diodes.
A semiconducting device is connected in a series circuit with a battery and a resistance. A current is found to pass through the circuit. If the polarity of the battery is reversed, the current drops to almost zero. The device may be
  • an intrinsic semiconductor
  • a p-type semiconductor
  • an n-type semiconductor
  • a p-n junction.
An AND gate can be prepared by repetitive use of 
  • NOT gate
  • OR gate
  • NAND gate
  • NOR gate
To reduce the ripples in a rectifier circuit with capacitor filter
  • $${R}_{L}$$ should be increased
  • input frequency should be decreased
  • input frequency should be increased
  • capacitors with high capacitance should be used
The most non-polluting and efficient lighting device is:
  • CFL
  • LED
  • Fluorescent light
  • Electric bulb
Two $$PN-$$ junctions can be connected in series by three different methods as shown in the figure. If the potential difference in the junctions is the same, then the correct connections will be 
1820606_7700b6494195423bb2bbbb47d93027fd.png
  • In the circuit (1) and (2)
  • In the circuit (2) and (3)
  • In the circuit (1) and (3)
  • Only in the circuit (1)
In an $$NPN$$ transistor circuit, the collector current is $$10\ mA$$. If $$90^o$$ of the electrons emitted reach the collector, the emitter current $$(i_E)$$ and base current $$(i_B)$$ are given by
  • $$i_E=-1\ mA, i_B=9\ mA$$
  • $$i_E=9\ mA, i_B=-1\ mA$$
  • $$i_E=1\ mA, i_B=11\ mA$$
  • $$i_E=11\ mA, i_B=1\ mA$$
If $$l_1, l_2, l_3$$ are the length of the emitter, base and collector of a transistor then
  • $$l_1=l_2=l_3$$
  • $$l_1 < l_2 > l_3$$
  • $$l_1 < l_2 < l_3$$
  • $$l_3 > l_1 > l_2$$
A $$PN$$- junction has a thickness of order of 
  • $$1\ cm$$
  • $$1\ mm$$
  • $$10^{-6}\ m$$
  • $$10^{-12}\ cm$$
In a transistor configuration $$\beta$$ parameter is
  • $$\dfrac {l_b}{l_c}$$
  • $$\dfrac {l_c}{l_b}$$
  • $$\dfrac {l_c}{l_a}$$
  • $$\dfrac {l_a}{l_c}$$
A hole in a $$P-$$ type semiconductor is
  • An excess electron
  • A missing electron
  • A missing atom
  • A donor level
When the electrical conductivity of a semi-conductor is due to the breaking of its covalent bonds, then the semiconductor is said to be
  • Donar
  • Aceptor
  • Intrinsic
  • Exterinsic
Bonding in a germanium crystal (semi-conductor) is
  • Metallic
  • Ionic
  • Vander Waal's type
  • Covalent
The laptop PC's modern electronic watches and calculator use the following for display
  • Single crystal
  • Poly crystal
  • Liquid crystal
  • Semiconductors
Electrical conductivity of a semiconductor
  • Decrease with the rise in its temperature
  • Increase with the rise in its temperature
  • Does not change with the rise in its temeprature
  • First increases and then decreases with the rise in its temperature
In good conductors of electricity, the type of bonding that exists is
  • Ionic
  • Vander Waals
  • Covalent
  • Metallic
Holes are charge carriers in 
  • Intrinsic semiconductors
  • Ionic solids
  • $$P-$$ type semiconductor
  • Metals
Zener breakdown in a semi-conductor diode occurs when 
  • Forward current exceeds certain value
  • Reverse bias exceeds certain value
  • Forward bias exceeds certain value
  • Potential barrier is reduced to zero
The most commonly used material for making transistor is
  • Copper
  • Silicon
  • Ebonite
  • Silver
In the study of transistor as an amplifier, if $$\alpha =I_c / I_e$$ and $$\beta =I_c /I_b$$, where $$I_c, I_b$$ and $$l$$ are the collector base and emitter currents, then 
  • $$\beta =\dfrac {1-\alpha}{\alpha}$$
  • $$\beta =\dfrac {\alpha}{1-\alpha}$$
  • $$\beta =\dfrac {\alpha}{1+\alpha}$$
  • $$\beta =\dfrac {1+\alpha}{\alpha}$$
The intrinsic semiconductor becomes an insulator at
  • $$0^{o}C$$
  • $$-100^{o}C$$
  • $$300\ K$$
  • $$0\ K$$
Given below are symbols for some logic gates
The $$XOR$$ gate and $$NOR$$ gate respectively are
1820777_53ec4421e50f40a3b80201ad9c86f916.png
  • $$1$$ and $$2$$
  • $$2$$ and $$3$$
  • $$3$$ and $$4$$
  • $$1$$ and $$4$$
Given below are four logic fate symbol (figure). Those for $$OR, NOR$$ and $$NAND$$ are respectively
1820784_5bdf033af05f4c8795c5b44b4a649f8a.png
  • $$1,4,3$$
  • $$4,1,2$$
  • $$1,3,4$$
  • $$4,2,1$$
When the $$P$$ end of $$P-N$$ junction is connected to the negative terminal of battery and the $$N$$ end to the positive terminals of the battery, then the $$P-N$$ junction behaves like 
  • A conductor
  • An insulator
  • A super-conductor
  • A semi-conductor
Function of rectifier is 
  • To convert $$ac$$ into $$dc$$
  • To convert $$dc$$ into $$ac$$
  • Both (a) and (b)
  • None of these
Which is the correct diagram of a half-wave rectifier 
Select the correct statement
  • In a full wave rectifier, two diodes work alternatively
  • In a full wave rectifier, two diodes work simultaneously
  • The efficiency of full wave and half wave rectifiers is same
  • The full wave rectifier is bi-directional.
A logic gate is an electric  
  • Makes logic decision
  • Allows electrons flow only in one direction
  • Work binary algebra
  • Alternates between $$0$$ and $$1$$ values
The impurity atom added to germanium to make in $$N-$$ type semiconductor is
  • Arsenic
  • Iridium
  • Aluminium
  • Iodine
The given truth table is of
$$A\quad 0\quad 1$$
$$X\quad 1\quad 0$$
  • $$OR$$ gate
  • $$AND$$ gate
  • $$NOT$$ gate
  • None of these
Symbol 
1820857_93d34c133d724997a0c3bd236cdb8983.png
  • $$NAND$$ gate
  • $$NOR$$ gate
  • $$NOT$$ gate
  • $$XNOR$$ gate
The correct symbol for zener diode is 
0:0:1


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