Q1: What is a Programmable Logic Controller (PLC)?
Ans: A PLC is an electronic device used to control machines and industrial processes automatically using programmed instructions.
Q2: State the uses of PLC.
Ans: Uses of PLC are:
- ➔ Industrial automation
- ➔ Machine control
- ➔ Process control systems
- ➔ Traffic control systems
Q3: State any six advantages of PLC.
Ans: Advantages of PLC are:
- ➔ High reliability
- ➔ Easy to program
- ➔ Less wiring required
- ➔ Flexible operation
- ➔ Easy maintenance
- ➔ Fast operation
Q4: State the limitations of PLC.
Ans: Limitations of PLC are:
- ➔ High initial cost
- ➔ Requires skilled programmer
- ➔ Limited for small applications
- ➔ Needs proper environment
Q5: Define Logic.
Ans: Logic is the process of making decisions based on given conditions.
Q6: Define Ladder Logic.
Ans: Ladder logic is a graphical programming language used in PLC that resembles a ladder diagram.
Q7: Define Rungs.
Ans: Rungs are the horizontal lines in a ladder logic diagram where instructions are written.
Q8: Define Relay Logic.
Ans: Relay logic is a control system that uses relays to perform logical operations.
Q9: State the basic components of PLC.
Ans: The basic components of PLC are:
- ➔ Central Processing Unit (CPU)
- ➔ Programming Keyboard and Monitor
- ➔ Input and Output Modules
Q10: Briefly explain the working of PLC.
Ans: PLC receives input signals from sensors.
The CPU processes the program logic.
Then it sends output signals to control devices like motors and relays.
Q11: What are Logic Gates?
Ans: Logic gates are electronic circuits that perform logical operations on one or more inputs to produce an output.
Q12: Name the types of Logic Gates.
Ans: Types of logic gates are:
- ➔ AND Gate
- ➔ OR Gate
- ➔ NOT Gate
- ➔ NAND Gate
- ➔ NOR Gate
- ➔ XOR Gate
- ➔ XNOR Gate
Q13: What is an AND Gate?
Ans: An AND gate gives output HIGH only when all inputs are HIGH.
Q14: State the uses of AND Gate.
Ans: Uses of AND gate are:
- ➔ Used in control circuits
- ➔ Used in safety systems
- ➔ Used in digital circuits
Q15: What is an OR Gate?
Ans: An OR gate gives output HIGH if any one input is HIGH.
Q16: State the uses of OR Gate.
Ans: Uses of OR gate are:
- ➔ Used in alarm systems
- ➔ Used in control circuits
- ➔ Used in decision making circuits
Q17: What is a NAND Gate?
Ans: A NAND gate gives output LOW only when all inputs are HIGH.
Q18: State the uses of NAND Gate.
Ans: Uses of NAND gate are:
- ➔ Used in digital circuits
- ➔ Used as universal gate
- ➔ Used in logic design
Q19: What is a NOR Gate?
Ans: A NOR gate gives output HIGH only when all inputs are LOW.
Q20: State the uses of NOR Gate.
Ans: Uses of NOR gate are:
- ➔ Used as universal gate
- ➔ Used in digital circuits
- ➔ Used in memory circuits
Q21: What is an XNOR Gate?
Ans: An XNOR gate gives output HIGH when inputs are equal.
Q22: State the uses of XNOR Gate.
Ans: Uses of XNOR gate are:
- ➔ Used in comparators
- ➔ Used in equality checking circuits
- ➔ Used in digital systems
Q23: What is a NOT Gate?
Ans: A NOT gate gives the opposite output of the input.
Q24: State the uses of NOT Gate.
Ans: Uses of NOT gate are:
- ➔ Used for signal inversion
- ➔ Used in digital circuits
- ➔ Used in logic design
Q25: What is an XOR Gate?
Ans: An XOR gate gives output HIGH when inputs are different.
Q26: State the uses of XOR Gate.
Ans: Uses of XOR gate are:
- ➔ Used in adders
- ➔ Used in error detection
- ➔ Used in digital circuits
Q27: What is a Digital Number System?
Ans: A digital number system is a method of representing numbers using digits.
Q28: What is the Decimal Number System?
Ans: Decimal number system uses base 10 and digits from 0 to 9.
Q29: What is the Binary Number System?
Ans: Binary number system uses base 2 and digits 0 and 1.
Q30: What is the Octal System?
Ans: Octal number system uses base 8 and digits from 0 to 7.
Q31: What is the Hexa-Decimal Number System?
Ans: Hexadecimal system uses base 16 and digits 0–9 and A–F.
Q32: Define Positive Logic.
Ans: Positive logic means HIGH voltage represents 1 and LOW voltage represents 0.
Q33: Define Negative Logic.
Ans: Negative logic means LOW voltage represents 1 and HIGH voltage represents 0.
Q34: What is the Truth Table?
Ans: A truth table is a table that shows all possible input combinations and their corresponding outputs.
Q35: Convert (14)10 into Binary.
Ans: Step 1:
Divide 14 by 2 → remainder 0
Step 2:
Divide 7 by 2 → remainder 1
Step 3:
Divide 3 by 2 → remainder 1
Step 3:
Divide 1 by 2 → remainder 1
Write remainders in reverse order:
(14)10 = (1110)2
Q36: Convert (0.101)2 into Decimal Number.
Ans: Step 1:
1 × 2-1 = 0.5
Step 2:
0 × 2-2 = 0
Step 3:
1 × 2-3 = 0.125
Add values:
0.5 + 0 + 0.125 = 0.625
(0.101)2 = (0.625)10
Q37: Convert (1101)2 into Decimal Number.
Ans: Step 1:
1 × 23 = 8
Step 2:
1 × 22 = 4
Step 3:
0 × 21 = 0
Step 4:
1 × 20 = 1
Add values:
8 + 4 + 0 + 1 = 13
(1101)2 = (13)10
Q38: How can we convert Decimal Number into Octal Number.
Ans: To convert decimal to octal:
Step 1:
Divide the number by 8
Step 2:
Note the remainder
Step 3:
Continue division until quotient is 0
Step 4:
Write remainders in reverse order to get octal number
