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Physics M.C.Q (1 Marks)

Electronics · MP Board (MPBSE) STD 12 Science (Madhya Pradesh - English Medium). 413 questions.

Questions · Page 3 of 9

M.C.Q (1 Marks)

MCQ 1011 Mark
In a diode valve the cathode temperature must be (f = work function)
  • A
    High and ∅ should be high
  • ✓
    High and ∅ should be low
  • C
    Low and ∅ should be high
  • D
    Low and ∅ should be high
Answer
Correct option: B.
High and ∅ should be low
High and ∅ should be low
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MCQ 1021 Mark
The ripple factor in a half wave rectifier is
  • ✓
    1.21
  • B
    0.48
  • C
    0.6
  • D
    None of these
Answer
Correct option: A.
1.21
 1.21
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MCQ 1031 Mark
The transconductance of a triode amplifier is 2.5 mili mho having plate resistance of 20 KW, amplification 10. Find the load resistance
  • ✓
    5 kW
  • B
    25 kW
  • C
    20 kW
  • D
    50 kW
Answer
Correct option: A.
5 kW
5 kW
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MCQ 1041 Mark
The slope of plate characteristic of a vacuum diode is $2 \times 10^{-2} mA / V$. The plate resistance of diode will be
  • A
    $50 \ W$
  • ✓
    $50 \ kW$
  • C
    $500 \ kW$
  • D
    $500 \ kW$
Answer
Correct option: B.
$50 \ kW$
(b) $50 \ kW$
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MCQ 1051 Mark
The amplification factor of a triode is 50. If the grid potential is decreased by 0.20 V, what increase in plate potential will keep the plate current unchanged
  • A
    5 V
  • ✓
     10 V
  • C
     0.2 V
  • D
     50 V
Answer
Correct option: B.
 10 V
 10 V
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MCQ 1061 Mark
The thermionic emission of electron is due to
  • A
    Electromagnetic field
  • B
    Electrostatic field
  • ✓
    High temperature
  • D
    Photoelectric effect
Answer
Correct option: C.
High temperature
 High temperature
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MCQ 1071 Mark
In a triode valve the amplification factor is $20$ and mutual conductance is $10^{-3} \ce{mho}.$ The plate resistance is
  • A
    $ 2 \times 10^3 \mathrm{~W} $
  • B
    $ 4 \times 10^3 \mathrm{~W} $
  • ✓
    $ 2 \times 10^4 \mathrm{~W} $
  • D
    $ 2 \times 10^4 \mathrm{~W}$
Answer
Correct option: C.
$ 2 \times 10^4 \mathrm{~W} $
$ 2 \times 10^4 \mathrm{~W} $
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MCQ 1081 Mark
The voltage gain of a triode depends upon
  • A
     Filament voltage
  • B
     Plate voltage
  • ✓
     Plate resistance
  • D
     Plate current
Answer
Correct option: C.
 Plate resistance
Plate resistance
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MCQ 1091 Mark
The electrical circuits used to get smooth d.c. output from a rectifier circuit is called
  • A
    Filter
  • ✓
    Amplifier
  • C
    Full wave rectifier
  • D
    Oscillator
Answer
Correct option: B.
Amplifier
Amplifier
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MCQ 1101 Mark
For a given triode μ = 20. The load resistance is 1.5 times the anode resistance. The maximum gain will be
  • A
     16
  • ✓
    12
  • C
    10
  • D
    None of the above
Answer
Correct option: B.
12
 12
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MCQ 1111 Mark
Diode is used as a/an
  • A
    Oscillator
  • B
    Amplifier
  • ✓
    Rectifier
  • D
     Modulator
Answer
Correct option: C.
Rectifier
 Rectifier
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MCQ 1121 Mark
Plate resistance of two triode valves is 2 KW and 4 KW, amplification factor of each of the valves is 40. The ratio of voltage amplification, when used with 4 KW load resistance, will be
  • A
    $10$
  • B
    $\frac{4}{3}$
  • ✓
    $\frac{3}{4}$
  • D
    $\frac{16}{3}$
Answer
Correct option: C.
$\frac{3}{4}$
$\frac{3}{4}$
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MCQ 1131 Mark
In a diode valve, the state of saturation can be obtained easily by
  • A
     High plate voltage and high filament current
  • ✓
    Low filament current and high plate voltage
  • C
    Low plate voltage and high cathode temperature
  • D
     High filament current and high plate voltage
Answer
Correct option: B.
Low filament current and high plate voltage
Low filament current and high plate voltage
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MCQ 1141 Mark
When plate voltage in diode valve is increased from 100 volt to 150 volt then plate current increases from 7.5 mA to 12 mA. The dynamic plastic resistance will be
  • A
    10 kW
  • ✓
    11 kW
  • C
    15 kW
  • D
    11.1 kW
Answer
Correct option: B.
11 kW
 11.1 kW
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MCQ 1151 Mark
A 2V battery is connected across the points A and B as shown in the figure given below. Assuming that the resistance of each diode is zero in forward bias and infinity in reverse bias, the current supplied by the battery when its positive terminal is connected to A is
  • ✓
     0.2 A
  • B
     0.4 A
  • C
     Zero
  • D
     0.1 A
Answer
Correct option: A.
 0.2 A
 0.2 A
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MCQ 1161 Mark
Which one is correct relation for thermionic emission
 
  • A
    $J=A T^{1 / 2} e^{-\emptyset / k T}$
  • ✓
    $J = AT ^2 e ^{-\varnothing / kT }$
  • C
    $J=A T^{3 / 2} e^{-\emptyset / k T}$
  • D
    $J=A T^2 e^{-\emptyset / 2 k T}$
Answer
Correct option: B.
$J = AT ^2 e ^{-\varnothing / kT }$
(b) $J = AT ^2 e ^{-\varnothing / kT }$
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MCQ 1171 Mark
Following is the relation between current and charge $I = AT ^2 e ^{ qt / v _{ L }}$ then value of $V _{ L }$ will be
  • A
    $\frac{ V }{ kT }$
  • B
    $\frac{ kV }{ T }$
  • ✓
    $\frac{ kT }{ v }$
  • D
    $\frac{ VT }{ k }$
Answer
Correct option: C.
$\frac{ kT }{ v }$
(c) $\frac{ kT }{ v }$
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MCQ 1181 Mark
Correct relation for triode is
 
  • ✓
    $\mu=g_m \times r_p$
  • B
    $\mu=\frac{g_m}{r_p}$
  • C
    $\mu=2 g_{ m } \times r _{ p }$
  • D
    None of these
Answer
Correct option: A.
$\mu=g_m \times r_p$
(a) $\mu=g_m \times r_p$
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MCQ 1191 Mark
Coating of strontium oxide on Tungsten cathode in a valve is good for thermionic emission because
  • ✓
    Work function decreases
  • B
    Work function increases
  • C
    Conductivity of cathode increases
  • D
    Cathode can be heated to high temperature
Answer
Correct option: A.
Work function decreases
Work function decreases
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MCQ 1201 Mark
The value of plate current in the given circuit diagram will be
  • A
     3 mA
  • B
     8 mA
  • ✓
     13 mA
  • D
     18 mA
Answer
Correct option: C.
 13 mA
13 mA
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MCQ 1211 Mark
Before the saturation state of a diode at the plate voltages of 400 V and 200 V respectively the currents are $\mathrm{i}_1$ and $\mathrm{i}_2$ respectively. The ratio $i_1 / i_2$ will be
  • A
    $\sqrt{2/4}$
  • B
    $2\sqrt2$
  • ✓
    $2$
  • D
    $1/2$
Answer
Correct option: C.
$2$
$2$
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MCQ 1221 Mark
The introduction of a grid in a triode valve affects plate current by
  • A
    Making the thermionic emission easier at low temperature
  • B
    Releasing more electrons from the plate
  • C
    By increasing plate voltage
  • ✓
    By neutralising space charge
Answer
Correct option: D.
By neutralising space charge
By neutralising space charge
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MCQ 1231 Mark
With a change of load resistance of a triode, used as an amplifier, from 50 kilo ohms to 100 kilo ohms, its voltage amplification changes from 25 to 30. Plate resistance of the triode is
  • ✓
    25 kW
  • B
    75 kW
  • C
    7.5 kW
  • D
    2.5 kW
Answer
Correct option: A.
25 kW
25 kW
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MCQ 1241 Mark
The unit of mutual conductance of a triode valve is
  • ✓
    Siemen
  • B
    Ohm
  • C
    Ohm metre
  • D
    Joule Coulomb$^{-1}$
Answer
Correct option: A.
Siemen
Siemen
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MCQ 1251 Mark
The triode constant is out of the following
  • A
    Plate resistance
  • B
    Amplification factor
  • C
    Mutual conductance
  • ✓
    All the above
Answer
Correct option: D.
All the above
All the above
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MCQ 1261 Mark
For a triode, at $v _{ g }=-1$ volt, the following observations were taken $v _{ p }=75 V, I _{ p }=2 mA, V _{ p }=100 V, I _{ p }=4 mA$. The value of plate resistance will be
  • A
    $25$ kW
  • B
    $20.8$ kW
  • ✓
    $12.5$ kW
  • D
    $100$ kW
Answer
Correct option: C.
$12.5$ kW
(c) $12.5$ kW
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MCQ 1271 Mark
If the amplification factor of a triode (m) is 22 and its plate resistance is 6600 ohm, then the mutual conductance of this valve is mho is
  • ✓
    $\frac{1}{300}$
  • B
    $25 \times 10^{-2}$
  • C
    $2.5 \times 10^{-2}$
  • D
    $0.25 \times 10^{-2}$
Answer
Correct option: A.
$\frac{1}{300}$
(a) $\frac{1}{300}$
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MCQ 1281 Mark
In the circuit of a triode valve, there is no change in the plate current, when the plate potential is increased from 200 volt to 220 volt and the grid potential is decreased from – 0.5 volt to –1.3 volt. The amplification factor of this valve is
  • A
    15
  • B
    20
  • ✓
    25
  • D
    35
Answer
Correct option: C.
25
25
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MCQ 1291 Mark
$14 \times 10^{15}$ electrons reach the anode per second. If the power consumed is 448 milliwatts, then the plate (anode) voltage is
  • A
    150 V
  • ✓
    200V
  • C
    14 × 448 V
  • D
    448/14V
Answer
Correct option: B.
200V
(b) 200V
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MCQ 1301 Mark
The slope of plate characteristic of a vacuum tube diode for certain operating point on the curve is $10^{-3} \frac{ mA }{ V }$. The plate resistance of the diode and its nature respectively
  • A
    $100$ kilo-ohms static
  • ✓
    $1000$ kilo-ohms static
  • C
    $1000$ kilo-ohms dynamic
  • D
    $100$ kilo-ohms dynamic
Answer
Correct option: B.
$1000$ kilo-ohms static
(b) $1000$ kilo-ohms static
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MCQ 1311 Mark
The amplification factor of a triode valve is 15. If the grid voltage is changed by 0.3 volt the change in plate voltage in order to keep the plate current constant (in volt) is
  • A
    0.02
  • B
    0.002
  • ✓
    4.5
  • D
    5.0
Answer
Correct option: C.
4.5
4.5
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MCQ 1321 Mark
In a triode valve
  • A
    If the grid voltage is zero then plate current will be zero
  • B
    If the temperature of filament is doubled, then the thermionic current will also be doubled
  • ✓
    If the temperature of filament is doubled, then the thermionic current will nearly be four times
  • D
    At a definite grid voltage the plate current varies with plate voltage according to Ohm’s law
Answer
Correct option: C.
If the temperature of filament is doubled, then the thermionic current will nearly be four times
If the temperature of filament is doubled, then the thermionic current will nearly be four times
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MCQ 1331 Mark
The combination of the gates shown in the figure below produces
  • A
     NOR gate
  • ✓
    OR gate
  • C
    AND gate
  • D
    XOR gate
Answer
Correct option: B.
OR gate
OR gate
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MCQ 1341 Mark
To get an output 1 from the circuit shown in the figure, the input must be
  • A
    A = 0, B = 1, C = 0
  • B
     A = 1, B = 0, C = 0
  • ✓
     A = 1, B = 0, C = 1.
  • D
     A = 1, B = 1, C = 0
Answer
Correct option: C.
 A = 1, B = 0, C = 1.
 A = 1, B = 0, C = 1
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MCQ 1351 Mark
In a triode amplifier, the value of maximum gain is equal to
  • A
     Half the amplification factor
  • ✓
    Amplification factor
  • C
    Twice the amplification factor
  • D
    Infinity
Answer
Correct option: B.
Amplification factor
 Amplification factor
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MCQ 1361 Mark
In an experiment, the saturation in the plate current in a diode is observed at 240V. But a student still wants to increase the plate current. It can be done, if
  • A
     The plate voltage is increased further
  • B
     The plate voltage is decreased
  • C
     The filament current is decreased
  • ✓
    The filament current is increased
Answer
Correct option: D.
The filament current is increased
The filament current is increased
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MCQ 1371 Mark
The amplification produced by a triode is due to the action of
  • A
     Filament
  • B
    Cathode
  • ✓
    Grid
  • D
    Plate
Answer
Correct option: C.
Grid
Grid
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MCQ 1381 Mark
For a triode $r_P=10$ kilo ohm and $g_m=3$ milli mho. If the load resistance is double of plate resistance, then the value of voltage gain will be(a) 10(b) 20(c) 15(d) 30
  • A
    $10$
  • ✓
    $20$
  • C
    $15$
  • D
    $30$
Answer
Correct option: B.
$20$
$20$
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MCQ 1391 Mark
The amplification factor of a triode is 20. If the grid potential is reduced by 0.2 volt then to keep the plate current constant its plate voltage is to be increased by
  • A
     10 volt
  • ✓
     4 volt
  • C
     40 volt
  • D
     100 volt
Answer
Correct option: B.
 4 volt
4 volt
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MCQ 1401 Mark
In a triode amplifier, $\mu=25, r_P=40$ kilo ohm and load resistance $R_L=10$ kilo ohm. If the input signal voltage is 0.5 volt, then output signal voltage will be
  • A
    $1.25$ volt
  • B
    $5$ volt
  • ✓
    $2.5$ volt
  • D
    $10$ volt
Answer
Correct option: C.
$2.5$ volt
(c) $2.5$ volt
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MCQ 1411 Mark
The amplification factor of a triode is 20 and trans-conductance is 3 milli mho and load resistance $3 \times 10^4 \Omega$, then the voltage gain is
  • ✓
    16.36
  • B
    28
  • C
    78
  • D
    108
Answer
Correct option: A.
16.36
(a) 16.36
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MCQ 1421 Mark
If $\mathrm{R}_{\mathrm{p}}=7 \mathrm{~K} \Omega, \mathrm{gm}=2.5$ millimho, then on increasing plate voltage by 50 V, how much the grid voltage is changed so that plate current remains the same
  • ✓
    – 2.86 V
  • B
    – 4 V
  • C
    + 4 V
  • D
    + 2 V
Answer
Correct option: A.
– 2.86 V
(a) – 2.86 V
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MCQ 1431 Mark
For a given plate-voltage, the plate current in a triode is maximum when the potential of
  • A
     The grid is positive and plate is negative
  • ✓
    The grid is positive and plate is positive
  • C
    The grid is zero and plate is positive
  • D
    The grid is negative and plate is positive
Answer
Correct option: B.
The grid is positive and plate is positive
 The grid is positive and plate is positive
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MCQ 1441 Mark
In an amplifier the load resistance $\mathrm{R}_{\mathrm{L}}$ is equal to the plate resistance ($\mathrm {r_p}$). The voltage amplification is equal to
  • A
    μ
  • B
    2 μ
  • ✓
    μ/2
  • D
    μ/4
Answer
Correct option: C.
μ/2
(c) μ/2
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MCQ 1451 Mark
The grid voltage of any triode valve is changed from –1 volt to – 3 volt and the mutual conductance is $3 \times 10^{-4}$ mho. The change in plate circuit current will be
  • A
    0.8 mA
  • ✓
    0.6 mA
  • C
    0.4 mA
  • D
    1 mA
Answer
Correct option: B.
0.6 mA
(b) 0.6 mA
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MCQ 1461 Mark
In diode, when there is saturation current, the plate resistance  $(r_p)$ is
  • A
    Zero
  • ✓
    Infinite
  • C
    Some finite quantity
  • D
    Data is insufficient
Answer
Correct option: B.
Infinite
Infinite
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MCQ 1471 Mark
Number of secondary electrons emitted per number of primary electrons depends on
  • A
    Material of target
  • B
     Frequency of primary electrons
  • ✓
     Intensity
  • D
     None of the above
Answer
Correct option: C.
 Intensity
Intensity
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MCQ 1481 Mark
Thermionic emission from a heated filament varies with its temperature $T$ as
  • A
    $T ^{-1}$
  • B
    $T$
  • ✓
    $T ^2$
  • D
    $T^{3 / 2}$
Answer
Correct option: C.
$T ^2$
(c) $T ^2$
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MCQ 1491 Mark
Which of the following logic gate is an universal gate
  • A
    OR
  • B
     NOT
  • C
     AND
  • ✓
    NOR
Answer
Correct option: D.
NOR
 NOR
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MCQ 1501 Mark
Sum of the two binary numbers $(10000)_2$ and $(11011)_2$ is
  • ✓
    $(111101)_2$
  • B
    $(1111111)_2$
  • C
    $(101111)_2$
  • D
    $(111001)_2$
Answer
Correct option: A.
$(111101)_2$
(a) $(111101)_2$
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