7976187520
Topic: Basic Digital Electronics and Boolean Function
1.What is the basic building block of digital
circuits?
a) Resistor
b) Capacitor
c) Logic Gates
d) Transformer
2.Which gate is known as the "Universal Gate"?
a) AND
b) OR
c) NAND
d) NOT
3.What is the output of an AND gate when both
inputs are 1?
a) 0
b) 1
c) Undefined
d) 10
4.Which Boolean law states: A + A = A?
a) Identity Law
b) Idempotent Law
c) Distributive Law
d) Complement Law
7976187520
5.What is the output of a NOR gate when both
inputs are 0?
a) 0
b) 1
c) Undefined
d) None of the above
6.Which of the following is the truth table of an
XOR gate?
a) Output is 1 only if both inputs are 1
b) Output is 1 if inputs are different
c) Output is always 0
d) Output is always 1
7.Simplify the Boolean expression: A · (B + C)
a) AB + AC
b) A + B + C
c) (AB)C
d) A + BC
8.What is the dual of the Boolean expression: A + 1
= 1?
a) A · 1 = A
b) A · 0 = 0
c) A · 1 = 1
d) A + 0 = A
7976187520
9.What is the minimum number of NAND gates
required to implement an OR gate?
a) 1
b) 2
c) 3
d) 4
10. What is the logic expression for a 3-input OR
gate?
a) A · B · C
b) A + B + C
c) A ⊕ B ⊕ C
d) A · (B + C)
11. Which logic gate produces an output opposite
to the input?
a) OR
b) AND
c) NOT
d) XOR
12. What is the output of the Boolean function F =
A + 0?
a) A
b) 0
c) 1
d) Undefined
7976187520
13. Which gate is represented by the equation F =
AB'?
a) AND
b) OR
c) NOR
d) AND-NOT
14. What is the simplified form of the expression:
A(A + B)?
a) A
b) B
c) AB
d) A + B
15. How many rows are there in the truth table of
a 3-input logic gate?
a) 4
b) 6
c) 8
d) 16
16. What does De Morgan's first theorem state?
a) (A · B)' = A' + B'
b) (A + B)' = A' · B'
c) A + A' = 1
d) A · 1 = A
7976187520
17. Which logic gate is equivalent to a bubbled
AND gate?
a) OR
b) NAND
c) NOR
d) XOR
18. What is the Boolean result of A · A'?
a) 0
b) 1
c) A
d) A'
19. What does a flip-flop circuit store?
a) 1 bit of data
b) 2 bits of data
c) 4 bits of data
d) 8 bits of data
20. What is the Boolean expression for a 2-input
XNOR gate?
a) AB + A'B'
b) AB' + A'B
c) A + B
d) AB' + A'B + AB
7976187520
Solution With Answer:
1.c) Logic Gates
Digital circuits are constructed using logic gates,
which perform basic operations like AND, OR, and
NOT.
2.c) NAND
NAND gates are called "Universal Gates" as they can
be used to construct all other logic gates.
3.b) 1
The output of an AND gate is 1 only when all inputs
are 1.
4.b) Idempotent Law
The Idempotent Law states A + A = A, which
simplifies redundant terms.
5.b) 1
The output of a NOR gate is 1 only when all inputs
are 0.
6.b) Output is 1 if inputs are different
XOR produces 1 only when inputs differ (e.g., 0 and
1 or 1 and 0).
7.a) AB + AC
By applying the distributive law: A⋅(B+C)=AB+AC
7976187520
8.c) A · 1 = 1
The dual of A+1=1 is A⋅1=A.
9.b) 2
Two NAND gates are required to implement an OR
gate.
10. b) A + B + C
A 3-input OR gate outputs 1 if any of the inputs A, B,
or C is 1.
11. c) NOT
The NOT gate inverts the input, making 0 into 1 and
1 into 0.
12. a) A
F=A+0 simplifies to A since adding 0 doesn't change
the value.
13. d) AND-NOT
F=AB′ represents an AND-NOT gate, where B is
inverted before ANDing with A.
14. a) A
A(A+B) simplifies to A due to the absorption law.
15. c) 8
A 3-input truth table has 2^3 = 8 rows.
7976187520
16. a) (A · B)' = A' + B'
De Morgan’s first theorem states (A⋅B)′ is equivalent
to A′+B′.
17. c) NOR
A bubbled AND gate is equivalent to a NOR gate.
18. a) 0
A⋅A′=0 because A′ is the complement of A, and they
cannot both be 1.
19. a) 1 bit of data
A flip-flop stores a single bit (1 or 0) of data.
20. a) AB + A'B'
The Boolean expression for a 2-input XNOR gate is
AB+A′B′, as it outputs 1 when inputs are the same.
