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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 2 of 9

M.C.Q (1 Marks)

MCQ 511 Mark
The plate current in a triode is given by $I_p=0.004\left(V_p+10 V_g\right)^{3 / 2} mA$ where $I_p . V_p$ and $V_g$ are the values of plate current, plate voltage and grid voltage, respectively. What are the triode parameters $m , r _{ p }$ and $g _{ m }$ for the operating point at $V_p=120$ volt and $V_{ g }=-2$ volt ?
  • ✓
     10, 16.7 kW, 0.6 m mho
  • B
    15, 16.7 kW, 0.06 m mho
  • C
     20, 6 kW, 16.7 m mho
  • D
     None of these
Answer
Correct option: A.
 10, 16.7 kW, 0.6 m mho
10, 16.7 kW, 0.6 m mho
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MCQ 521 Mark
A change of 0.8 mA in the anode current of a triode occurs when the anode potential is changed by 10 V. If m = 8 for the triode, then what change in the grid voltage would be required to produce a change of 4 mA in the anode current
  • ✓
    6.25
  • B
    0.16 V
  • C
     15.2 V
  • D
    (d) None of these
Answer
Correct option: A.
6.25
 6.25 V
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MCQ 531 Mark
A metallic surface with work function of 2 eV, on heating to a temperature of 800 K gives an emission current of 1 mA. If another metallic surface having the same surface area, same emission constant but work function 4 eV is heated to a temperature of 1600 K, then the emission current will be
  • A
    1 mA
  • B
    2 mA
  • ✓
    4 mA
  • D
    None of these
Answer
Correct option: C.
4 mA
 4 mA
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MCQ 541 Mark
In the circuit given below, V(t) is the sinusoidal voltage source, voltage drop $V_{A B}(t)$ across the resistance R is
  • A
    Is half wave rectified
  • B
    Is full wave rectified
  • C
    Has the same peak value in the positive and negative half cycles
  • ✓
    Has different peak values during positive and negative half cycle
Answer
Correct option: D.
Has different peak values during positive and negative half cycle
(d) Has different peak values during positive and negative half cycle
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MCQ 551 Mark
The plate characteristic curve of a diode in space charge limited region is as shown in the figure. The slope of curve at point P is 5.0 mA/V. The static plate resistance of diode will be
  • A
    111.1$\Omega$
  • B
    222.2$\Omega$
  • ✓
    333.3$\Omega$
  • D
    444.4$\Omega$
Answer
Correct option: C.
333.3$\Omega$
(c) 333.3$\Omega$
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MCQ 561 Mark
The junction diode in the following circuit requires a minimum current of 1 mA to be above the knee point (0.7 V) of its I-V characteristic curve. The voltage across the diode is independent of current above the knee point. If $V_B=5 V$, then the maximum value of R so that the voltage is above the knee point, will be
  • ✓
    4.3 k$\Omega$
  • B
    860 k$\Omega$
  • C
    4.3$\Omega$
  • D
    860$\Omega$
Answer
Correct option: A.
4.3 k$\Omega$
(a) 4.3 k$\Omega$
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MCQ 571 Mark
The value of amplification factor from the following graph will be
  • ✓
    10
  • B
    50
  • C
    25
  • D
    40
Answer
Correct option: A.
10
(a) 10
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MCQ 591 Mark
A sinusoidal voltage of peak value 200 volt is connected to a diode and resistor R in the circuit shown so that half wave rectification occurs. If the forward resistance of the diode is negligible compared to R the rms voltage (in volt) across R is approximately
  • A
    200
  • ✓
    100
  • C
    $\frac{200}{\sqrt{2}}$
  • D
    280
Answer
Correct option: B.
100
100
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MCQ 601 Mark
In the following common emitter configuration an NPN transistor with current gain b = 100 is used. The output voltage of the amplifier will be
  • A
    10 mV
  • B
    0.1 V
  • ✓
    1.0 V
  • D
    10 V
Answer
Correct option: C.
1.0 V
(c) 1.0 V
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MCQ 611 Mark
The variation of anode current in a triode corresponding to a change in grid potential at three different values of the plate potential is shown in the diagram. The mutual conductance of the triode is
  • ✓
    2.5 m mho
  • B
    5.0 m mho
  • C
    7.5 m mho
  • D
    10.0 m mho
Answer
Correct option: A.
2.5 m mho
(a) 2.5 m mho
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MCQ 621 Mark
In a negative logic the following wave form corresponds to the
  • A
    0000000000
  • B
    0101101000
  • C
    1111111111
  • ✓
    1010010111
Answer
Correct option: D.
1010010111
(d) 1010010111
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MCQ 631 Mark
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 milliwatts. What should be the value of the resistor R, connected in series with the diode for obtaining maximum current
  • A
    1.5 $\Omega$
  • ✓
    5 $\Omega$
  • C
    6.67 $\Omega$
  • D
    200 $\Omega$
Answer
Correct option: B.
5 $\Omega$
(b) 5 $\Omega$
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MCQ 641 Mark
The i-V characteristic of a P-N junction diode is shown below. The approximate dynamic resistance of the P-N junction when a forward bias of 2volt is applied
  • A
     1 W
  • ✓
     0.25 W
  • C
     0.5 W
  • D
     5 W
Answer
Correct option: B.
 0.25 W
 0.25 W
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MCQ 651 Mark
A source voltage of 8V drives the diode in fig. through a current-limiting resistor of 100 ohm. Then the magnitude of the slope load line on the V-I characteristics of the diode is
  • ✓
    0.01
  • B
    100
  • C
    0.08
  • D
    12.5
Answer
Correct option: A.
0.01
(a) 0.01
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MCQ 661 Mark
The relation between dynamic plate resistance $\left(r_p\right)$ of a vacuum diode and plate current in the space charge limited region, is
  • A
    $r_p \propto I_p$
  • B
    $r_p \propto I_p^{3 / 2}$
  • C
    $r_p \propto \frac{1}{I_p}$
  • ✓
    $r_p \propto \frac{1}{\left( I _{ p }\right)^{1 / s }}$
Answer
Correct option: D.
$r_p \propto \frac{1}{\left( I _{ p }\right)^{1 / s }}$
(d) $r_p \propto \frac{1}{\left( I _{ p }\right)^{1 / s }}$
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MCQ 671 Mark
The plate current $i_p$ in a triode valve is given $i_p=K\left(V_p+\mu V_g\right)^{3 / 2}$ where $i_p$ is in milliampere and $V_p$ and $V_g$ are in volt. If $r_p=10^4$ ohm, and $g_m=5 \times 10^{-3} mho$, then for $i_p=8 mA^2$ and $V_p=300$ volt, what is the value of $K$ and grid cut off voltage
  • A
    $-6 V,(30)^{3 / 2}$
  • ✓
    $-6 V,(1 / 30)^{3 / 2}$
  • C
    $+6 V,(30)^{3 / 2}$
  • D
    $+6 V,(1 / 30)^{3 / 2}$
Answer
Correct option: B.
$-6 V,(1 / 30)^{3 / 2}$
(b) $-6 V,(1 / 30)^{3 / 2}$
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MCQ 681 Mark
The diagram of a logic circuit is given below. The output F of the circuit is represented by
  • A
    W.(X + Y)
  • B
    W.(X.Y)
  • ✓
    W + (X.Y)
  • D
    W + (X + Y)
Answer
Correct option: C.
W + (X.Y)
(c) W + (X.Y)
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MCQ 691 Mark
The shows two NAND gates followed by a NOR gate. The system is equivalent to the following logic gate
  • A
    OR
  • ✓
    AND
  • C
    NAND
  • D
    None of these
Answer
Correct option: B.
AND
AND
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MCQ 711 Mark
The combination of gates shown below produces
  • A
     AND gate
  • B
     XOR gate
  • C
     NOR gate
  • ✓
     NAND gate
Answer
Correct option: D.
 NAND gate
 NAND gate
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MCQ 721 Mark
In $\text{NPN}$ transistor, $10^{10}$ electrons enters in emitter region in $10^{-6}$ sec. If $2\%$ electrons are lost in base region then collector current and current amplification factor $(b)$ respectively are
  • ✓
    $1.57 \ mA, 49$
  • B
    $1.92 \ mA, 70$
     
  • C
    $2 \ mA, 25$
  • D
    $2.25 \ mA, 100$
Answer
Correct option: A.
$1.57 \ mA, 49$
$1.57 \ mA, 49$
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MCQ 731 Mark
For the transistor circuit shown below, if b = 100, voltage drop between emitter and base is 0.7 V then value of $\mathrm{V}_{\mathrm{CE}}$ will be
  • A
    10 V
  • B
    5 V
  • ✓
    13 V
  • D
    0 V
Answer
Correct option: C.
13 V
(c) 13 V
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MCQ 741 Mark
In the circuit shown in figure the maximum output voltage $V_0$ is
  • A
    0 V
  • ✓
    5 V
  • C
    10 V
  • D
    $\frac{5}{\sqrt{2}} V$
Answer
Correct option: B.
5 V
(b) 5 V
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MCQ 751 Mark
Ge and Si diodes conduct at 0.3 V and 0.7 V respectively. In the following figure if Ge diode connection are reversed, the valve of $V_0$ changes by
  • A
    0.2 V
  • ✓
    0.4 V
  • C
    0.6 V
  • D
    0.8 V
Answer
Correct option: B.
0.4 V
(b) 0.4 V
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MCQ 761 Mark
The contribution in the total current flowing through a semiconductor due to electrons and holes are $\frac{3}{4}$ and $\frac{1}{4}$ respectively. If the drift velocity of electrons is $\frac{5}{2}$ times that of holes at this temperature, then the ratio of concentration of electrons and holes is
  • ✓
     $6: 5$
  • B
     $5: 6$
  • C
     $3: 2$
  • D
     $2: 3$
Answer
Correct option: A.
 $6: 5$
 6 : 5
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MCQ 771 Mark
A potential difference of 2 V is applied between the opposite faces of a Ge crystal plate of area $1 cm^2$ and thickness 0.5 mm . If the concentration of electrons in Ge is $2 \times 10^{19} / m ^3$ and mobilities of electrons and holes are $0.36 \frac{ m ^2}{\text { volt-sec }}$ and $0.14 \frac{ m ^2}{\text { volt-sec }}$ respectively, then the current flowing through the plate will be
  • A
    0.25 A
  • B
    0.45 A
  • C
    0.56 A
  • ✓
    0.64 A
Answer
Correct option: D.
0.64 A
0.64 A
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MCQ 781 Mark
A diode is connected to 220 V (rms) ac in series with a capacitor as shown in figure. The voltage across the capacitor is
  • A
    $220\ V$
  • B
    $110\ V$
  • C
    $311.1\ V$
  • ✓
    $\frac{220}{\sqrt 2}V$
Answer
Correct option: D.
$\frac{220}{\sqrt 2}V$
$\frac{220}{\sqrt 2}V$
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MCQ 801 Mark
The circuit shown in following figure contains two diode $\mathrm{D}_1$ and $\mathrm{D}_2$ each with a forward resistance of 50 ohms and with infinite backward resistance. If the battery voltage is 6 V, the current through the 100 ohm resistance (in amperes) is
  • A
    Zero
  • ✓
    0.02
  • C
    0.03
  • D
    0.036
Answer
Correct option: B.
0.02
(b) 0.02
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MCQ 811 Mark
In the following circuits PN-junction diodes $D_1, D_2$ and $D_3$ are ideal for the following potential of A and B, the correct increasing order of resistance between A and B will be
(i) – 10 V, – 5V (ii) – 5V, – 10 V (iii) – 4V, – 12V
  • A
     (i) < (ii) < (iii)
  • ✓
     (iii) < (ii) < (i)
  • C
    (ii) = (iii) < (i)
  • D
    (i) = (iii) < (ii)
Answer
Correct option: B.
 (iii) < (ii) < (i)
 (b) (iii) < (ii) < (i)
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MCQ 821 Mark
The Bohr radius of the fifth electron of phosphorus (atomic number = 15) acting as dopant in silicon (relative dielectric constant = 12) is
  • ✓
    10.6 Å
  • B
    0.53 Å
  • C
    21.2 Å
  • D
    None of these
Answer
Correct option: A.
10.6 Å
 10.6 Å
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MCQ 831 Mark
A transistor is used as an amplifier in CB mode with a load resistance of 5 k W the current gain of amplifier is 0.98 and the input resistance is 70 W, the voltage gain and power gain respectively are
  • ✓
    70, 68.6
  • B
    80, 75.6
  • C
    60, 66.6
  • D
    90, 96.6
Answer
Correct option: A.
70, 68.6
 70, 68.6
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MCQ 841 Mark
The peak voltage in the output of a half-wave diode rectifier fed with a sinusoidal signal without filter is 10 V. The dc component of the output voltage is
  • A
    $10 / \sqrt{2} V$
  • ✓
    $10 / p V$
  • C
    $10 V$
  • D
    $20 / p V$
Answer
Correct option: B.
$10 / p V$
 10/p V
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MCQ 851 Mark
The grid in a triode valve is used
  • A
    To increases the thermionic emission
  • ✓
    To control the plate to cathode current
  • C
    To reduce the inter-electrode capacity
  • D
    To keep cathode at constant potential
Answer
Correct option: B.
To control the plate to cathode current
(b) To control the plate to cathode current
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MCQ 861 Mark
Current in the circuit will be
  • A
    $\frac{5}{40} A$
  • ✓
    $\frac{5}{50} A$
  • C
    $\frac{5}{10} A$
  • D
     $\frac{5}{20} A$
Answer
Correct option: B.
$\frac{5}{50} A$
$\frac{5}{50} A$
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MCQ 871 Mark
A P-type semiconductor has acceptor levels $57$ meV above the valence band. The maximum wavelength of light required to create a hole is (Planck's constant $h =6.6 \times 10^{-34} J$-s)
  • A
    $57 A^0$
  • B
    $57 \times 10^{-3} A^0$
  • ✓
    $217100 A^0$
  • D
    $11.61 \times 10^{-33} A^0$
Answer
Correct option: C.
$217100 A^0$
(c) $217100 A^0$
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MCQ 881 Mark
In the circuit, if the forward voltage drop for the diode is 0.5V, the current will be
  • ✓
    $3.4\ mA$
  • B
    $2\ mA$
  • C
    $2.5\ mA$
  • D
    $3\ mA$
Answer
Correct option: A.
$3.4\ mA$
$3.4\ mA$
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MCQ 891 Mark
When a potential difference is applied across, the current passing through
  • A
    An insulator at 0 K is zero
  • B
    A semiconductor at 0 K is zero
  • C
    A P-N diode at 300 K is finite, if it is reverse biased
  • ✓
    a, b, c
Answer
Correct option: D.
a, b, c
 a, b, c
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MCQ 901 Mark
In PN-junction diode the reverse saturation current is $10^{-5} amp$ at $27^{\circ} C$ The forward current for a voltage of 0.2 volt is $\left[\exp (7.62)=2038.6, K=1.4 \times 10^{-23} J / K \right]$
  • A
    $2037.6 \times 10^{-3} amp$
  • B
    $203.76 \times 10^{-3} amp$
  • ✓
    $20.376 \times 10^{-3} amp$
  • D
    $2.0376 \times 10^3 amp$
Answer
Correct option: C.
$20.376 \times 10^{-3} amp$
(c) $20.376 \times 10^{-3} amp$
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MCQ 911 Mark
Figure gives a system of logic gates. From the study of truth table it can be found that to produce a high output (1) at R, we must have
  • A
    X = 0, Y = 1
  • B
    X = 1, Y = 1
  • ✓
    X = 1, Y = 0
  • D
    X = 0, Y = 0
Answer
Correct option: C.
X = 1, Y = 0
 X = 1, Y = 0
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MCQ 921 Mark
The following configuration of gate is equivalent to
  • A
     NAND
  • ✓
     XOR
  • C
    OR
  • D
     None of these
Answer
Correct option: B.
 XOR
XOR
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MCQ 931 Mark
The typical ionisation energy of a donor in silicon is
  • A
    10.0 eV
  • B
    1.0eV
  • ✓
    0.1 eV
  • D
    0.001 eV
Answer
Correct option: C.
0.1 eV
0.1 eV
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MCQ 941 Mark
The probability of electrons to be found in the conduction band of an intrinsic semiconductor at a finite temperature
  • ✓
    Decreases exponentially with increasing band gap
  • B
    Increases exponentially with increasing band gap
  • C
    Decreases with increasing temperature
  • D
    Is independent of the temperature and the band gap
Answer
Correct option: A.
Decreases exponentially with increasing band gap
(a) Decreases exponentially with increasing band gap
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MCQ 951 Mark
In the following circuit find $\mathrm{I}_1$ and $\mathrm{I}_2$
  • A
    0, 0
  • B
    5 mA, 5 mA
  • C
    5 mA, 0
  • ✓
    0, 5 mA
Answer
Correct option: D.
0, 5 mA
(d) 0, 5 mA
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MCQ 961 Mark
A silicon speciman is made into a P-type semi-conductor by dopping, on an average, one Indium atom per $5 \times 10^7$ silicon atoms. If the number density of atoms in the silicon specimen is $5 \times 10^{28}$ atoms $/ m ^3$ then the number of acceptor atoms in silicon per cubic centimetre will be
  • A
    $2.5 \times 10^{30}$ atoms $/ cm ^3$
  • B
    $1.0 \times 10^{13}$ atoms $/ cm ^3$
  • ✓
    $1.0 \times 10^{15}$ atoms $/ cm ^3$
  • D
    $2.5 \times 10^{36}$ atoms $/ cm ^3$
Answer
Correct option: C.
$1.0 \times 10^{15}$ atoms $/ cm ^3$
(c) $1.0 \times 10^{15}$ atoms $/ cm ^3$
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MCQ 971 Mark
Select the correct statement
  • ✓
    In a full wave rectifier, two diodes work alternately
  • B
    In a full wave rectifier, two diodes work simultaneously
  • C
    The efficiency of full wave and half wave rectifiers is same
  • D
    The full wave rectifier is bi-directional
Answer
Correct option: A.
In a full wave rectifier, two diodes work alternately
(a) In a full wave rectifier, two diodes work alternately
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MCQ 981 Mark
The current in a triode at anode potential $100 V$ and grid potential $– 1.2 V$ is $7.5 mA$. If grid potential is changed to $– 2.2 V,$ the current becomes $5.5 mA.$ the value of trans conductance $(g_m)$ will be
  • ✓
    $2$ mili mho
  • B
    $3$ mili mho
  • C
    $4$ mili mho
  • D
    $0.2$ mili mho
Answer
Correct option: A.
$2$ mili mho
$2$ mili mho
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MCQ 991 Mark
Plate voltage of a triode is increased from 200 V to 225 V. To maintain the plate current, change in grid voltage from 5V to 5.75 V is needed. The amplification factor is 
  • A
    40
  • B
    45
  • ✓
    33.3
  • D
    25
Answer
Correct option: C.
33.3
 33.3
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MCQ 1001 Mark
The plate resistance of a triode is $2.5 \times 10^4 W$ and mutual conductance is $2 \times 10^{-3} \ce{mho}.$ What will be the value of amplification factor
  • ✓
    $50$
  • B
    $1.25 \times 10^7$
  • C
    $75$
  • D
    $2.25 \times 10^7$
Answer
Correct option: A.
$50$
$50$
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