Semiconductors(12th Grade > Physics ) Questions and answers for exam Preparation

12th Grade > Physics

SEMICONDUCTORS MCQs

Total Questions : 30 | Page 3 of 3 pages

Question 21. In the circuit as shown in figure, A and B represent two inputs and C represents the

OR gate
NOR gate
AND gate
NAND gate
35 mA

Discuss Question

Answer: Option A. -> OR gate
:
A
The circuit represents OR gate, as the output at C is 1, when either A or B or both A and B have input at level 1. But output at C is zero, when both A and B are at zero level and the Boolean expression is C = (A + B).

Question 22. A p-n junction (D) shown in the figure can act as a rectifier. An alternating current source (V) is connected in the circuit. The current (I) in the resistor (R) can be shown by

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Answer: Option B. -> b
:
B
The given circuit works is half wave rectifier. In this circuit, we will get current through R when p-n junction diode is forward biased and no current when p-n junction is reversed biased. Thus the current through resistance will be shown by graph (b).

Question 23. Current gain

β_{A C}

in common emitter mode of transistor is

βAC=△IC△IB,VC=constant
βAC=△IB△IC,VC=constant
βAC=△IC△IE,VC=constant
βAC=△IE△IC,VC=constant

Discuss Question

Answer: Option A. -> βAC=△IC△IB,VC=constant
:
A
It is

β_{A C} = \frac{△ I_{C}}{△ I_{B}}, V_{C} = c o n s t a n t

Collector voltage is to be kept a constant.

Question 24. In common base mode of transistor, the collector current is 5.488 mA for an emitter current of 5.60 mA. The value of the base current amplification factor

(β)

will be

48
49
50
51
35 mA

Discuss Question

Answer: Option B. -> 49
:
B

I_{b} = I_{e} - I_{c}

= 5.60 - 5.488 = 0.112mA

β = \frac{I_{e}}{I_{b}} = \frac{5.488}{0.112}

= 49.

Question 25. How many NAND gates are used in an OR gate?

Four
Two
Three
Five

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Answer: Option C. -> Three
:
C
For this purpose we use three NAND gate in manner as shown. The first two NAND gates are operated as NOT gates and their outputs are fed to the third. The resulting circuit is OR gate.

How Many NAND Gates Are Used In An OR Gate?

Question 26. The current I through 10

Ω

resistor in the circuit shown in figure.

The Current I Through 10 Ω Resistor In The Circuit Shown In...

50 mA
20 mA
40 mA
80 mA
35 mA

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Answer: Option D. -> 80 mA
:
D
In the given circuit, junction diode

D_{1}

if forward biased, will conduct current and junction diode

D_{2}

is reverse biased, will not conduct current. Therefore, current
I =

\frac{2}{10 + 15}

= 0.08 A = 80 mA.

Question 27. To get an output Y = 1 from the circuit shown in figure the inputs A, B and C must be respectively

1, 0, 1
1, 1, 0
0, 1, 0
1, 0, 0

Discuss Question

Answer: Option A. -> 1, 0, 1
:
A
The output of OR gate is
Y’ = (A + B)
The output and AND gate is
Y = Y’ . C = (A + B) . C
IfA = 1, B = 0, C = 1, they Y = (1 + 0). 1 = 1

Question 28. Current gain in common base configuration is less than 1 because

Discuss Question

Answer: Option C. -> Ic
:
C