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1.

What are the values of the inputs to a three-input OR gate, if its output is 0?

Answer»
XYzY=X+Y+Z
0000
2.

What are the values of the inputs to a three-input NAND gate, if its output is 0?

Answer»
XYz(XYZ)’
1110
3.

For the truth table given below, what type of logic gate does the output X represent?ABCX00010011010101111001101111011110

Answer»

The type of logic gate that the output X represent is NAND.

4.

Prove the following rules using the proof by perfect induction.1. XY’ + XY = X2. X+Y=Y+X

Answer»

1. XY’ + XY = X
By proof of perfect induction X = 0, Y =1
XY’ + XY = X
LHS = 0.0 + 0.1 = 0 + 0 = 0
By proof of perfect induction X = 1, Y = 0
LHS = 1.1 + 1.0 = 1 + 0 = 1.

2. X + Y = Y + X
By proof of perfect induction X = 0, Y = 1
LHS = 0 + 1 = 1
RHS = 1 + 0=1
LHS = RHS
By proof of perfect induction X = 1, Y = 0
LHS = 1 + 0 = 1
RHS = 0 + 1 = 1
LHS = RHS

5.

Give the dual form of:1. 0.X + X.Y + 1.X2. X.(Y+Z) = X.Y + X.Z3. X + X’.Y = X + Y4. 1 + X = 1

Answer»

The dual form of

  1. 0.X + X.Y + 1.X   is 1 + X’. X’ + Y’. 0 + X’
  2. X.(Y+Z) = X.Y + X.Z  is  X’ + (Y’.Z’) = X’ + Y’. X’ + Z’
  3. X + X’.Y = X + Y  is  X’. X + Y’ = X’. Y’
  4. 1 + X = 1  is  0.X = X.
6.

Simplify the following logical expression using De Morgan’s theorems.

Answer»

1. (A + B).C
= AC + BC.

2. (A + BC). (D + EF)
(A + BC) . D + (A + BC). EF
AD + BCD + AEF + BCEF.

7.

State De Morgan’s theorems.

Answer»

1. De Morgan’s theorem 1:
When the OR sum of two variables is inverted, this is the same as inverting each variable individually and then ANDing these inverted variables.
(X + Y)’ = X’. Y’

2. De Morgan’s theorem 2:
When the AND product of two variables is inverted, this is the same as inverting each variable individually and then ORing them.
(X.Y)’ = X’ + Y’

8.

State the principle duality of theorems in Boolean algebra.

Answer»

The principle of duality theorems states that starting with a Boolean relation another Boolean relation can be derived by.

  1. Changing each OR sign (+) to and AND sign (.)
  2. Changing each AND sign (.) to an OR sign (+)
  3. Changing each 0 by 1 and each 1 by 0.
9.

Mention the three basic logic gates.

Answer»

The three basic logic gates are NOT, OR and AND gate.

10.

Mention different universal gates.

Answer»

The different universal gates are NAND and NOR.

11.

What is meant by universal gates?

Answer»

A gate which can be used to create any Logic gate is called Universal Gate.

12.

What is a truth table?

Answer»

A table that represents all possible values of logical variables along with all the possible results of the given combinations of values.

13.

Write the truth table for NOT gate.

Answer»
AY = A’
01
10
14.

Which are the three logic operations?

Answer»

The three logic operations are Nor, Or and And.

15.

Write the truth table for AND gate.

Answer»
ABY = A.B
000
010
100
111
16.

Write the NOT gate rule, (write the output conditions)

Answer»

The NOT gate is an electronic circuit that produces an inverted version of the input as its output. It is also known as an inverter.

AY=A’
01
10
17.

Write the OR gate rule, (write the output conditions)

Answer»

The OR gate is an electronic circuit that gives a high output (1) if one or more of its inputs are high.

ABY=A+B
000
011
101
111
18.

Write the truth table for OR gate.

Answer»
AB Y = A+B
000
011
101
111
19.

Write the AND gate rule. (Write the output conditions)

Answer»

The AND gate is an electronic circuit that gives a high output (1) only if all its inputs are high.

ABY=A.B
000
010
100
111