length of collector is greater than that of emitter

both emitter and collector have same length

length of emitter is greater than that of collector

any one of emitter and collector can have greater length

MCQ Questions for Class 12 Medical Physics Semiconductor Electronics: Materials, Devices And Simple Circuits Quiz 15

When a semiconductor is heated, its resistance.

0%
Remains the same
0%
Decreases
0%
Increases
0%
May increases or decreases depending on the semiconductor

Truth table for the given circuit will be

Explanation

$x$	$y$	$\overline{x}$	$a=x.y$	$b=\overline{x}.y$	$z=\overline{a.b}$
0	0	1	0	0	1
0	1	1	0	1	1
1	0	0	0	0	1
1	1	0	1	0	1

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:

0%
$12\ V$
0%
$11\ V$
0%
$11.3\ V$
0%
$11.7\ V$

Explanation

Ge conducts at

$0.3\ V$ and

$Si$ Conducts at

$0.7\ V$ . Both

$Ge$ and

$Si$ are connected in parallel. When current begins to flow, then the potential difference remains at

$0.3\ V$ , so no current flows through Si-diode.

$\therefore$ Potential difference across resistive load

$= 12 - 0.3$

$= 11.7\ V$

$\therefore$ Potential of

$Y = 11.7\ V$ .

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

0%
$4.24Sm^{-1}$
0%
$2.12Sm^{-1}$
0%
$1.09Sm^{-1}$
0%
$0.47Sm^{-1}$

Explanation

Given in question,

Mobilities of electrons

$\mu_e=0.36\times m^2V^{-1}s^{-1}$

Mobilities o holes

$\mu_h=0.17\times m^2V^{-1}s^{-1}$

densities of electron

$=$ densities of holes

$=2.5\times10^{19}m^{-3}$

As we know, conductivity,

$\sigma = \dfrac{1}{p}=e({\mu}_e n_e+{\mu}_n n_n)$

$=1.6\times 10^{-19}[0.36\times2.5\times10^{19}+0.17\times2.5\times 10^{19})]$

$=2.12 Sm^{-1}$

So the electrical conductivies of germanium is

$2.12Sm^{-1}$

With the help of the arrangement shown in figure which of the following gates could be realised?

0%
OR
0%
NAND
0%
AND
0%
NOR

Which of the following is NOT true about a zener diode?

0%
It is used as a voltage regulator.
0%
It is forward biased.
0%
It is reverse biased.
0%
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.

0%
$3 \times 10^ 6Hz$
0%
$1 \times 10^ 6Hz$
0%
$30 \times 10^ 6Hz$
0%
$4 \times 10^ 6Hz$

In a common emitter transistor circuit, the base current is

$40 \mu A$ then

${ V }_{ BE }$ is:

0%
2 v
0%
0.2 v
0%
0.8 v
0%
zero

If the lattice constant of this semiconductor is decreased, then which of the following is correct?

0%
All $E_{c}, E_{g}, E_{v}$ increase
0%
$E_{c}$ and $E_{v}$ increases but $E_{g}$ decrease
0%
$E_{c}$ and $E_{v}$ decreases but $E_{g}$ increase
0%
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

0%
20
0%
40
0%
60
0%
80

Explanation

Current gain

$=\left(\dfrac{I_C}{I_B}\right)\ keeping\ V_{CE}= constant$

Given ,

$I_C=1mA,I_B=50\mu A$

$\dfrac{I_C}{I_B}=20$

Hence option

$\textbf A$ is correct answer.

In the given circuit the current through the zener diode is.

0%
10 m A
0%
6.67 m A
0%
5 mA
0%
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

$6000\ A^o$ ?

0%
$D_{1}$
0%
$D_{2}$
0%
$D_{3}$
0%
$D_{1}$ and $D_{2}$ both

Explanation

Given that,

Band gap of ${{D}_{1}}=2.5\,eV$

Band gap of ${{D}_{2}}=2\,eV$

Band gap of ${{D}_{3}}=3\,eV$

Wave length $\lambda =6000\overset{\circ }{\mathop{A}}\,$

Now, the wave length for $2.5\ eV$

${{\lambda }_{1}}=\dfrac{hc}{E}$

${{\lambda }_{1}}=\dfrac{6.6\times {{10}^{-34}}\times 3\times {{10}^{8}}}{2.5\times 1.6\times {{10}^{-19}}}$

${{\lambda }_{1}}=4.95\times {{10}^{-7}}\,m$

Now, for $2\ eV$

${{\lambda }_{2}}=\dfrac{hc}{E}$

${{\lambda }_{2}}=\dfrac{6.6\times {{10}^{-34}}\times 3\times {{10}^{8}}}{2\times 1.6\times {{10}^{-19}}}$

${{\lambda }_{2}}=6.2\times {{10}^{-7}}\,m$

Now, for $3\ eV$

${{\lambda }_{3}}=\dfrac{hc}{E}$

${{\lambda }_{3}}=\dfrac{6.6\times {{10}^{-34}}\times 3\times {{10}^{8}}}{3\times 1.6\times {{10}^{-19}}}$

${{\lambda }_{3}}=4.13\times {{10}^{-7}}\,m$

For detection of optical signal the wave length of incident energy radiation must be greater.

So, only ${{D}_{2}}$ can detect the radiation

If the lattice constant of this semiconductor is decreased, then which of the following is correct?

0%
All $E_c, E_g, E_v$ increase
0%
$E_c$ and $E_v$ increase but $E_g$ decreases
0%
$E_c$ and $E_v$ decrease but $E_g$ incerases
0%
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:

0%
increase
0%
decrease
0%
remain constant
0%
first increase then decrease

Output of the circuit shown below will be :

0%
zero all the times
0%
like half wave rectifier with positive cycles in output
0%
like half wave rectifier with negative cycles in output
0%
like that of a full wave rectifier

The output in the figure is:-

0%
$\overline {AB}$
0%
$\overline {\overline A .\overline B }$
0%
$\overline {\overline {A.B} }$
0%
${\overline A .\overline B }$

For the given transistor circuit

$\mathrm { V } _ { \mathrm { BE } } = 0.7 \mathrm { V }$ . Find

$I _ { B }$

0%
$3.7 \mathrm { mA }$
0%
$2.2 \mathrm { mA }$
0%
$1.8 \mathrm { mA }$
0%
$1.5 \mathrm { mA }$

The current density (J) for an intrinsic semiconductor is given by which of the following equations?

0%
$j=n_1 . e . (\mu_e+\mu_h) . E$
0%
$j=n_1 . e . (\mu_e-\mu_h) . E$
0%
$j=\dfrac{n_1 . e . (\mu_e-\mu_h)} {E}$
0%
$j=\dfrac{E}{n_1 . e . (\mu_e+\mu_h)}$

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.

0%
$4.3 Sm^{-1}$
0%
$1.21 Sm^{-1}$
0%
$2.22 Sm^{-1}$
0%
$4.22 Sm^{-1}$

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 ..............

0%
A, C, B, D
0%
B, D, A, C
0%
A, B, C, D
0%
C, A, D, B

The I-V characteristic of an LED is

Explanation

$\textbf{Explanation:}$

When powered, a light-emitting diode (LED) is always a forward biassed contact diode that emits light. The creation of light energy is caused by the recombination of electrons and holes at the junction. Radiate in the infrared spectrum. If the light-emitting diode is reverse-biased, no light will be emitted at all. When an LED is reverse-biased, it might be damaged.

The spontaneous emission mechanism is used to emit light from a light-emitting diode. In a semiconductor, there are two energy bands. The valence band has a smaller energy band than the conduction band, which has a higher energy band.

$\textbf{Option A is correct.}$

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

0%
Zero
0%
Between zero and half
0%
Half
0%
One

The value of

$\beta$ for transistor, for which the value of

$\alpha =0.95,$ will be

0%
19
0%
24
0%
0.24
0%
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?

0%
200 $\Omega$
0%
6.67 $\Omega$
0%
5 $\Omega$
0%
1.5 $\Omega$

Silicon is a semiconductor. On adding a small quantity of arsenic to it its conductivity

0%
inceases
0%
decreases
0%
remaions the same
0%
becomes zero

Figure shows the particle realization of a logic gate. Identify the logic gate

0%
NAND
0%
NOR
0%
XOR
0%
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:

0%
${135^0}$
0%
${180^0}$
0%
${45^0}$
0%
${90^0}$

Explanation

Explanation: In CE amplifier cirucit the input and output voltage are out of phase. When the input voltage is increased then Rb is increased. Ic also increases so the voltage drop across Rc is increased. However increase in voltage across Rc is in opposite sense.

So, phase angle between them is

$180^0$ .
18

Option

$B$ is correct.

The adjoining logic symbol is equivalent to

0%
$OR$ gate
0%
$AND$ gate
0%
$NOT$ gate
0%
$NAND$ gate

The concentration of impurities in a transistor is

0%
Largest for base region
0%
Least for collector region
0%
Moderate for emitter region
0%
Largest for emitter region

Write down the boolean expression for output

$Y$ of system in figure

0%
$A \overset {-}{B} +\overset {-}{A} B$
0%
$(\overset {-}{A}+ \overset {-}{B})(A+B)$
0%
$\overset {-}{A} \overset {-}{B} + AB$
0%
$AB + (\overset {-}{A}+ \overset {-}{B})$

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

0%
NAND
0%
NOT
0%
AND
0%
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?

0%
It is a pnp transistor with R as collector
0%
It is a pnp transistor with R as emitter
0%
It is an npn transistor with R as collector
0%
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?

0%
The depletion region width decrease in comparison to unbaised case
0%
The electric field strength varies in depletion region
0%
The neutral regions behave like ohmic reisters with small resistance.
0%
The charge density in the depletion region is uniform.

In a transistor

0%
both emitter and collector have same length
0%
length of emitter is greater than that of collector
0%
length of collector is greater than that of emitter
0%
any one of emitter and collector can have greater length

In p - type semi conductor, there are

0%
immobile negative ions
0%
immobile positive ions
0%
no minority carriers
0%
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,

0%
400 mA
0%
200 mA
0%
100 mA
0%
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:

0%
$1k\Omega$
0%
$3k\Omega$
0%
$35k\Omega$
0%
$30\Omega$

The combined network of the following NOR gates will behaves as

0%
AND gate
0%
XOR gate
0%
NOR gate
0%
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 _.

0%
AND gate
0%
OR gate
0%
NOR gate
0%
NAND gate

For a diode connected in parallel with a resistor, which is the most likely current (I) -voltage (V) characteristics?

Explanation

When the value of V is +ve, the diode is forward biased. Thus, the current flowing through the diode is exponential and the current in the resistor varies linearly. Thus, the V−I characteristic is an exponential curve when

$V>0$

When the value of V is -ve, the diode is reverse biased. Thus, no current flows through it and the current in the resistor varies linearly with voltage (Ohm's law). Thus, the V−I characteristic is a straight line when

$V<0$

So, the correct answer is option (A).

C and Si both have a same lattice structure, having 4 bonding electrons in each. However, C is insulator whereas Si is intrinsic semiconductor:-

0%
In case of C the valance bond is not completely filled at absolute zero temperature
0%
In the case of C, the conduction band is partly filled even at zero temperature
0%
The four bonding electron in case of C lies in the second orbit whereas in case of Si lies in third orbit
0%
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 ?

0%
$A + \overline{A.B}$
0%
$A + A. B$
0%
$(A + B) . (\overline{A . B})$
0%
$(A + B) (\overline{A + B})$

In the transistor configuration,

$I_{1}, I_{2}$ and

$I_{3}$ are ammeter readings. Then

0%
$I_{1} > I_{2} > I_{3}$
0%
$I_{1} < I_{2} < I_{3}$
0%
$I_{2} > I_{3} > I_{1}$
0%
$I_{2} > I_{1} > I_{3}$
0%
$I_{1} = I_{2} = I_{3}$

Explanation

In the given

${\text{n - p - n}}$ transistor, clearly

${I_2} = {I_1} + {I_3}$

Also, in general, the value of

${I_1}$ is much less than

${I_2}$ or

${I_3}$ .

Hence,

${I_2} > {I_3} > {I_1}$

What is the output of the combination of the gates shown in fig. below ?

0%
$A + \overline{A . B}$
0%
$A + A. B$
0%
$(A + B) . (\overline{A. B})$
0%
$(A + B) (\overline{A + B})$

What is the output of the combination of the gates shown in fig. below ?

0%
$A + \overline{A . B}$
0%
$A + A. B$
0%
$(A + B) . (\overline{A . B})$
0%
$(A + B) (\overline{A + B})$

Which one is in forward bias :

0%
0%
0%
0%
None of these

Explanation

In forward bias of a diode the

$P$ -end must be connected to the positive terminal of the battery and the

$N$ -end is connected to the negative terminal of the battery.

So, option (B) is correct.

Which of the following P-N junction diode is reverse biased

Explanation

Current only flows from a higher potential to a lower potential. Also, the ends of the circuit that are grounded remain at zero potential.

In cases (A), (C) & (D), the diodes are connected in the forward bias.

In case (B), the

${\text{p - }}$ side is connected to the lower potential, and

${\text{n - }}$ side is connected to the higher potential, suggesting that the diode is in reverse bias.

In the given transistor circuit, the base current is

$35 \mu A$ . the value of

$R_b$ is -

0%
$100 k \Omega$
0%
$200 k \Omega$
0%
$300 k \Omega$
0%
$400 k \Omega$

Explanation

In the given loop, we can use KVL, and we can get-

$7 - \left( {35\mu A} \right).{R_b} = 0$

${R_b} = \frac{7}{{\left( {35 \times {{10}^{ - 6}}} \right)}} = 200000{\text{ }}\Omega = 200{\text{ k}}\Omega$

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.

0%
$2.16 \times 10^{19} /m^3$
0%
$4.64 \times 10^{18} /m^3$
0%
$10^{20} /m^3$
0%
$none\ of\ these$

Explanation

The resistivity of the semiconductor,

$\rho = 0.5{\text{ }}\Omega m$

The charge of electron,

${q_e} = 1.6 \times {10^{ - 19}}{\text{ C}}$

The electron mobility,

${\mu _e} = 0.39{\text{ }}{{\text{m}}^2}{{\text{V}}^{{\text{ - 1}}}}{{\text{s}}^{{\text{ - 1}}}}$

The hole mobility,

${\mu _h} = 0.19{\text{ }}{{\text{m}}^2}{{\text{V}}^{{\text{ - 1}}}}{{\text{s}}^{{\text{ - 1}}}}$

Now,

$\frac{1}{\mu } = {q_e}\left( {{n_i}{\mu _e} + {n_i}{\mu _h}} \right)$

${n_i} = \frac{1}{{\mu .{q_e}\left( {{\mu _e} + {\mu _h}} \right)}}$

${n_i} = \frac{1}{{\left( {0.5{\text{ }}\Omega m} \right).\left( {1.6 \times {{10}^{ - 19}}{\text{ C}}} \right)\left( {\left( {0.39 + 0.19} \right){{\text{m}}^2}{{\text{V}}^{{\text{ - 1}}}}{{\text{s}}^{{\text{ - 1}}}}} \right)}}$

${n_i} = 4.64 \times {10^{18}}{\text{ }}{{\text{m}}^{ - 3}}$

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

0:0:1

Practice Class 12 Medical Physics Quiz Questions and Answers

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

0:0:1

Practice Class 12 Medical Physics Quiz Questions and Answers

Support mcqexams.com by disabling your adblocker.