CBSE Questions for Class 12 Medical Physics Semiconductor Electronics: Materials, Devices And Simple Circuits Quiz 15 - MCQExams.com

When a semiconductor is heated, its resistance.
  • Remains the same
  • Decreases
  • Increases
  • May increases or decreases depending on the semiconductor
Truth table for the given circuit will be

870163_6e9dd56d309d43908f0e2d3eafb10ed5.png
Two junction diodes one of germanium $$(Ge)$$ and other of silicon $$(Si)$$ are connected as shown in figure to a battery of emf $$12\ v$$ and a load resistance $$10\ k\ \Omega$$. The germanium diode conducts at $$0.3\ V$$ and silicon diode at $$0.7\ V$$. When a current flows in the circuit, then the potential of terminal $$Y$$ will be:
669281_d6a0b884a98c49fba620a49628080610.jpg
  • $$12\ V$$
  • $$11\ V$$
  • $$11.3\ V$$
  • $$11.7\ V$$
Mobilities of electrons and holes in a sample of intrinsic germanium at room temperature are $$0.36m^2V^{-1}s^{-1}$$ and $$0.17m^2V^{-1}s^{-1}$$. The electron and hole densities are each equal to $$2.5\times 10^{19}m^3$$. The electrical conductivity of germanium is
  • $$4.24Sm^{-1}$$
  • $$2.12Sm^{-1}$$
  • $$1.09Sm^{-1}$$
  • $$0.47Sm^{-1}$$
With the help of the arrangement shown in figure which of the following gates could be realised?
996147_dc93ca1e7d644f7e88a07c9dd25d8129.png
  • OR
  • NAND
  • AND
  • NOR
Which of the following is NOT true about a zener diode?
  • It is used as a voltage regulator.
  • It is forward biased.
  • It is reverse biased.
  • It has a breakdown voltage.
In a diode detector, output circuit consist of $$R=1M\Omega \quad and\quad C=1pF$$. Calculate the carrier frequency it can detect.
  • $$3 \times 10^ 6Hz$$
  • $$1 \times 10^ 6Hz$$
  • $$30 \times 10^ 6Hz$$
  • $$4 \times 10^ 6Hz$$
In a common emitter transistor circuit, the base current is $$40 \mu A$$ then $${ V }_{ BE }$$ is:
1114042_324c701c0b094f45ad47e5be51a85326.png
  • 2 v
  • 0.2 v
  • 0.8 v
  • zero
If the lattice constant of this semiconductor is decreased, then which of the following is correct?
1093384_57cc357ec37a4e12bdaba71e91ef7e75.png
  • All $$E_{c}, E_{g}, E_{v}$$ increase
  • $$ E_{c}$$ and $$ E_{v}$$ increases but $$ E_{g}$$ decrease
  • $$ E_{c}$$ and $$ E_{v}$$ decreases but $$ E_{g}$$ increase
  • All $$E_{c}, E_{g}, E_{v}$$ decrease
In a transistor circuit, when the base current is increased by 50 $$\mu A$$, keeping the collector voltage fixed at 2V, the collector current increases by 1 mA. The current gain of the transistor is
  • 20
  • 40
  • 60
  • 80
In the given circuit the current through the zener diode is. 
1264766_292ea0814e874f2889ca46bf023db119.png
  • 10 m A
  • 6.67 m A
  • 5 mA
  • 3.33 mA
There photo dlodes $$D_{1}, D_{2}$$ and $$D_{3}$$ are made of semiconductor having band gap $$2.5\ eV, 2\ eV$$ and $$3\ eV$$ respectively. Which one will be able to detect light of wavelength $$6000\ A^o$$?
  • $$D_{1}$$
  • $$D_{2}$$
  • $$D_{3}$$
  • $$D_{1}$$ and $$D_{2}$$ both
If the lattice constant of this semiconductor is decreased, then which of the following is correct?
1205545_d4dfc1133c824949ba7840d43cad20f4.PNG
  • All $$E_c, E_g, E_v$$ increase
  • $$E_c$$ and $$E_v$$ increase but $$E_g$$ decreases
  • $$E_c$$ and $$E_v$$ decrease but $$E_g$$ incerases
  • All $$E_c, E_g, E_v$$ decrease
If the revers bias voltage applied  to a p-n junction diode is increased, its barrier capacitance would:
  • increase
  • decrease
  • remain constant
  • first increase then decrease
Output of the circuit shown below will be :
1134516_c3094fefb6f54e2b87e39e8cfadc3016.png
  • zero all the times
  • like half wave rectifier with positive cycles in output
  • like half wave rectifier with negative cycles in output
  • like that of a full wave rectifier
The output in the figure is:-

1216963_21e14e2a735741eeb89d7437c05ebabe.PNG
  • $$\overline {AB} $$
  • $$\overline {\overline A .\overline B } $$
  • $$\overline {\overline {A.B} } $$
  • $${\overline A .\overline B }$$
For the given transistor circuit $$\mathrm { V } _ { \mathrm { BE } } = 0.7 \mathrm { V }$$.  Find $$I _ { B }$$
1191171_5beccc2badef448cb9b1a90afc2d2e95.png
  • $$3.7 \mathrm { mA }$$
  • $$2.2 \mathrm { mA }$$
  • $$1.8 \mathrm { mA }$$
  • $$1.5 \mathrm { mA }$$
The current density (J) for an intrinsic semiconductor is given by which of the following equations?
  • $$j=n_1 . e . (\mu_e+\mu_h) . E$$
  • $$j=n_1 . e . (\mu_e-\mu_h) . E$$
  • $$j=\dfrac{n_1 . e . (\mu_e-\mu_h)} {E}$$
  • $$j=\dfrac{E}{n_1 . e . (\mu_e+\mu_h)} $$
The following data are for intrinsic germanium at 300 K. $$n_1 = 2.4 \times 10^{19} \ /m^3, \ \mu_e = 0.39m^2 \ / Vs, \ \mu_n = 0.19 m^2 \ /Vs$$. Calculate the conductivity of intrinsic germanium.
  • $$4.3 Sm^{-1}$$
  • $$1.21 Sm^{-1}$$
  • $$2.22 Sm^{-1}$$
  • $$4.22 Sm^{-1}$$
For the given circuit shown in fig to act as full wave rectifier - ac input should be connected across .......... and ........ the d.c. output would appear across ........ and ..............
1193645_7417da63c3484fbea96a94c4b6378bbe.png
  • A, C, B, D
  • B, D, A, C
  • A, B, C, D
  • C, A, D, B
The I-V characteristic of an LED is
The Fermi level of an intrinsic semiconductor is pinned at the centre of the band gap. The probability of occupation of the highest electron state in valence band at room temperature, will be
  • Zero
  • Between zero and half
  • Half
  • One
The value of $$ \beta $$ for transistor, for which the value of $$ \alpha =0.95, $$ will be
  • 19
  • 24
  • 0.24
  • 48
The diode used in the circuit shown in the figure has a constant voltage drog currents and a maximum power rating of 100 mW. What should be the value r, connected in series with the diode, for obtaining maximum current l?
1223885_1d1ea05002c74cf391c68e3b4b2844c0.PNG
  • 200 $$\Omega $$
  • 6.67 $$\Omega $$
  • 5 $$\Omega $$
  • 1.5 $$\Omega $$
Silicon is a semiconductor. On adding a small quantity of arsenic to it its conductivity 
  • inceases
  • decreases
  • remaions the same
  • becomes zero
Figure shows the particle realization of a logic gate. Identify the logic gate
1232158_eb30740a72f64cab9dc1af8ef84d5933.png
  • NAND
  • NOR
  • XOR
  • XNOR
In a common emitter amplifier circuit using an $$n-p-n$$ transistor, the phase difference between the input and the output voltages will be:
  • $${135^0}$$
  • $${180^0}$$
  • $${45^0}$$
  • $${90^0}$$
The adjoining logic symbol is equivalent to
1228877_9be4d65482bd43c2b3c5a1cac7bff406.PNG
  • $$OR$$ gate
  • $$AND$$ gate
  • $$NOT$$ gate
  • $$NAND$$ gate
The concentration of impurities in a transistor is
  • Largest for base region
  • Least for collector region
  • Moderate for emitter region
  • Largest for emitter region
Write down the boolean expression for output $$Y$$ of system in figure
1234198_294715ca0f9d413abcb158044a514398.png
  • $$A \overset {-}{B} +\overset {-}{A} B$$
  • $$(\overset {-}{A}+ \overset {-}{B})(A+B)$$
  • $$ \overset {-}{A} \overset {-}{B} + AB$$
  • $$ AB + (\overset {-}{A}+ \overset {-}{B})$$
If a,b,c,d are input to a gate and x is its ouput, then as per the following time graph, the gate is 
1293813_afdfd4f8b90141f0919896dfc8529541.png
  • NAND
  • NOT
  • AND
  • OR
A working transistor with its three legs marked P, Q and R is tested within a multimeter. No conduction is found between P and Q. By connecting the common (negative) terminal of the multimeter to R and the other (positive) terminal to P or Q, some resistance is seen on the multimeter. Which of following is true for the transistor?
  • It is a pnp transistor with R as collector
  • It is a pnp transistor with R as emitter
  • It is an npn transistor with R as collector
  • It is an npn transistor with R as base
A reverse-biased diode is
In a forward biased $$P-N$$ junction carrying a certain amount of current, which of the following statement is false?
  • The depletion region width decrease in comparison to unbaised case
  • The electric field strength varies in depletion region
  • The neutral regions behave like ohmic reisters with small resistance.
  • The charge density in the depletion region is uniform.
In a transistor 
  • both emitter and collector have same length
  • length of emitter is greater than that of collector
  • length of collector is greater than that of emitter
  • any one of emitter and collector can have greater length
 In p - type semi conductor, there are 
  • immobile negative ions
  • immobile positive ions
  • no minority carriers
  • holes as majority carriers
A p-n junction diode connected in series with a resistor of 200 $$\Omega $$ is forward biased so that a current 200 mA flows.If the voltage across this combination is instantaneously reversed at t=0, the current through diode is approximately,
  • 400 mA
  • 200 mA
  • 100 mA
  • 0 mA
A common-emitter amplifier gives an output of $$3V$$ for an input of $$0.01V$$. If $$\beta$$ of the transistor is $$100$$ and the input resistance is $$1k\Omega$$, then the collector resistance is:
  • $$1k\Omega$$
  • $$3k\Omega$$
  • $$35k\Omega$$
  • $$30\Omega$$
The combined network of the following NOR gates will behaves as
1358001_521cb5ec8da44fc6bf075b68c9dd25ef.png
  • AND gate
  • XOR gate
  • NOR gate
  • NAND gate
The logic which produces LOW output when one of the input is HIGH and produces HIGH output only when all its inputs are LOW is called _.
  • AND gate
  • OR gate
  • NOR gate
  • NAND gate
For a diode connected in parallel with a resistor, which is the most likely current (I) -voltage (V) characteristics?
1337483_69c0ff142860481499ac11f2ad28f9be.PNG
C and Si both have a same lattice structure, having 4 bonding electrons in each. However, C is insulator whereas Si is intrinsic semiconductor:-
  • In case of C the valance bond is not completely filled at absolute zero temperature
  •  In the case of C, the conduction band is partly filled even at zero temperature
  • The four bonding electron in case of C lies in the second orbit whereas in case of Si lies in third orbit
  • The four bonding electron in case of C lies in third orbit whereas for Si they lie in fourth orbit
What is the output of the combination of the gates shown in fig. below ?
1322039_e2a065f6176f4917b8e7ada6195aab7b.png
  • $$A + \overline{A.B}$$
  • $$A + A. B$$
  • $$(A + B) . (\overline{A . B})$$
  • $$(A + B) (\overline{A + B})$$
In the transistor configuration, $$I_{1}, I_{2}$$ and $$I_{3}$$ are ammeter readings. Then 
1361599_66101368ae1f4a77a4b1eb592fe29fce.png
  • $$I_{1} > I_{2} > I_{3}$$
  • $$I_{1} < I_{2} < I_{3}$$
  • $$I_{2} > I_{3} > I_{1}$$
  • $$I_{2} > I_{1} > I_{3}$$
  • $$I_{1} = I_{2} = I_{3}$$
What is the output of the combination of the gates shown in fig. below ?
1322041_00fed9517bff49e4b595319496ce7e0b.png
  • $$A + \overline{A . B}$$
  • $$A + A. B$$
  • $$(A + B) . (\overline{A. B})$$
  • $$(A + B) (\overline{A + B})$$
What is the output of the combination of the gates shown in fig. below ?
1322040_0805fa8cf3614a72955c0bd237753b1d.png
  • $$A + \overline{A . B}$$
  • $$A + A. B$$
  • $$(A + B) . (\overline{A . B})$$
  • $$(A + B) (\overline{A + B})$$
Which one is in forward bias :
  • None of these
Which of the following P-N junction diode is reverse biased
In the given transistor circuit, the base current is $$ 35 \mu A $$. the value of $$ R_b $$ is -
1394057_bb216fee0d9948deb550f4cc3a18b447.PNG
  • $$ 100 k \Omega $$
  • $$ 200 k \Omega $$
  • $$ 300 k \Omega $$
  • $$ 400 k \Omega $$

The resistivity of a pure semiconductor is  $$0.5 \Omega\ m$$. If the electron and hole mobility be $$0.39$$ $$m^2/V-s$$ and $$0.19$$ $$m^2/V-s$$ respectively then calculate the intrinsic carrier concentration.
  • $$2.16 \times 10^{19} /m^3$$
  • $$4.64 \times 10^{18} /m^3$$
  • $$ 10^{20} /m^3$$
  • $$none\ of\ these$$
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