Semiconductor Electronics: Materials, Devices and Simple Circuits Test 43

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Semiconductor Electronics: Materials, Devices and Simple Circuits Test 43

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Question 1
1 / -0

Which logic gate is represented by the following logic gates?

A
NOR

B
NAND

C
AND

D
OR

Solution

The initial two gates are the NOT gates. They provide the inverse of the input. The output of the NOT gate is fed to the NOR gate. So, the truth table for the inputs to the logic circuit is as given below:

Truth table:

A B Y
0 0 0
0 1 0
1 0 0
1 1 1

The truth table shown above is for the AND gate.
Question 2
1 / -0

Which of following gates produces output of $$1$$?

A

B

C

D

Solution

For (A), NAND Gate, output will be $$Y = \overline {1.1} = \bar 1 = 0$$
For (B), NOR Gate, output will be $$Y = \overline{0+0} = \bar 0 = 1$$
For (C), AND Gate, output will be $$Y= {1.0} = 0$$
For (D), OR Gate, output will be $$Y = {0+0} = 0$$

Hence, option (B) is the correct one.
Question 3
1 / -0

A hole is drilled in a copper sheet. The diameter of the hole is 4.24 cm at 27.0$$^{\circ}$$C. What is the change in the diameter of the hole when the sheet is heated to 227$$^{\circ}$$C? Coefficient of linear expansion of copper is 1.70 x 10$$^{-5}$$

A
$$1.44 \times 10^{-2}$$ cm

B
$$2.44 \times 10^{-3}$$ cm

C
$$1.44\times 10^{-2}$$mm

D
$$2.44 \times 10^{-3}$$ mm

Solution

$$D_2=4.24cm$$
Initial Area of the hole $$(A_0)=\pi r^2=22/7(4.24/2)^2\\=4.494\pi cm^2$$
Initial temp. $$(T_1)=27°=27+273=300K$$
Final temp. $$(T_2)=227°=227+273=500K$$
Coefficientof linear exp. $$(O)=1.7\times 10^{-5}/°C$$
Superficial expansion $$(b)=2\times $$ Linear expansion
$$=2\times1.7\times10^{-5}°C\\=3.4\times 10^{-5}°C$$
Use formula
$$A=A_0(1+b\Delta T)\\A=4.49\pi[1+3.4\times10^{-5}\times(500-300)]\\ A=4.494\pi[1+0.0068]\\A=4.525cm^2=\pi D 2^2/$\\B2^2=4.523\times4\\ D2=4.2544cm$$
Change in diameter $$=\Delta D=D_2-D_1\\=4.2544-4.24\\=0.0144cm$$
Question 4
1 / -0

When the source voltage increases in a zener regulator, which of these currents remains approximately constant?

A
Series current

B
Zener current

C
Load current

D
Total current

Solution

The load current is independent of the source voltage variations and hence remains a constant
Question 5
1 / -0

If the load resistance decreases in a zener regulator, the zener current

A
Decreases

B
Stays the same

C
Increases

D
Equals the source voltage divided by the series resistance

Solution

The load current is given by $$I_L=\dfrac{V_z}{R_L}$$ and the zener current is given by $$I_z=I_s-I_L$$. Thus, if the load resistance decreases, load current increases. This in turn will reduce the zener current
Question 6
1 / -0

The logic circuit shown in the figure represents characteristic of which logic gate?

A
OR gate

B
NOR gate

C
AND gate

D
NAND gate

Solution

$$C=A'+B'$$
By De-Morgan's theorem,
$$(AB)'=A'+B'\\ \therefore C=(AB)'$$
Therefore, NAND gate.
Question 7
1 / -0

What is true about the breakdown voltage in a zener diode?

A
It decreases when current increases.

B
It destroys the diode.

C
It equals the current times the resistance.

D
It is approximately constant.

Solution

As the current in the zener diode increases, the voltage across the diode remains constant. This voltage will be equal to the zener breakdown voltage
Question 8
1 / -0

The correct output for the given circuit is:

A

B

C

D

Solution

$$0-{T}_{0}$$ $$C=(\overline { 1+1 } .1)=0$$
$${T}_{0}-2{T}_{0}$$ $$C=(\overline { 1+1 } .1)=0$$
$$2{T}_{0}-\infty $$ $$C=(\overline { 1+0 } .1)=0$$
Question 9
1 / -0

The current flowing through the zener diode in figure is:

A
$$20\,mA$$

B
$$25\,mA$$

C
$$15\,mA$$

D
$$5\,mA$$

Solution

Using Kirchoff's current law:
$$\dfrac{{10 - 5}}{{500}} = {I_1} + \dfrac{5}{{1000}}$$
$$\dfrac{5}{{500}} - \dfrac{5}{{1000}} = {I_1}$$
$$\dfrac{{10 - 5}}{{1000}} = {I_1}$$
$$\boxed{5\,mA = {I_1}}$$
Question 10
1 / -0

The graph given represents the I-V characteristics of a Zener diode. Which part of the characteristic curve is most relevant for its operation as a voltage regulator?

A
$$ab$$

B
$$bc$$

C
$$cd$$

D
$$de$$

Solution

Hence ans should be $$de$$ bez zenve diode acts as voltage congulator is reverse biasing where in chore voltage tange called zener breatdown voltage