Day 11 – Chapter 2: Logic Gates
Class 11 Computer Science
2.15 Introduction to Logic Gates (लॉजिक गेट्स का परिचय)
Logic gates are the basic building blocks of digital electronics. They perform logical operations on binary inputs (0 or 1) to produce a binary output.
लॉजिक गेट्स डिजिटल इलेक्ट्रॉनिक्स के मूल घटक हैं। ये बाइनरी इनपुट (0 या 1) पर तार्किक संचालन करते हैं और बाइनरी आउटपुट उत्पन्न करते हैं।
2.16 Types of Logic Gates (लॉजिक गेट्स के प्रकार)
2.16.1 AND Gate (AND गेट)
The AND gate outputs 1 only when all inputs are 1.
AND गेट तब ही 1 का आउटपुट देता है जब सभी इनपुट 1 हों।
- Symbol: (AND Gate Symbol)
- Truth Table:
| Input A | Input B | Output (A × B) |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
2.16.2 OR Gate (OR गेट)
The OR gate outputs 1 when at least one input is 1.
OR गेट तब 1 का आउटपुट देता है जब कम से कम एक इनपुट 1 हो।
- Symbol: (OR Gate Symbol)
- Truth Table:
| Input A | Input B | Output (A + B) |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 1 |
2.16.3 NOT Gate (NOT गेट)
The NOT gate inverts the input. If the input is 1, the output is 0, and vice versa.
NOT गेट इनपुट को उलट देता है। यदि इनपुट 1 है, तो आउटपुट 0 होगा और इसके विपरीत।
- Symbol: (NOT Gate Symbol)
- Truth Table:
| Input A | Output (A’) |
|---|---|
| 0 | 1 |
| 1 | 0 |
2.16.4 XOR Gate (XOR गेट)
The XOR gate outputs 1 when exactly one of the inputs is 1.
XOR गेट तब 1 का आउटपुट देता है जब ठीक एक इनपुट 1 हो।
- Symbol: (XOR Gate Symbol)
- Truth Table:
| Input A | Input B | Output (A ⊕ B) |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 0 |
2.16.5 NAND Gate (NAND गेट)
The NAND gate outputs the complement of the AND gate. It outputs 0 only when all inputs are 1.
NAND गेट AND गेट का पूरक आउटपुट देता है। यह तभी 0 आउटपुट देता है जब सभी इनपुट 1 हों।
- Symbol: (NAND Gate Symbol)
- Truth Table:
| Input A | Input B | Output (A × B)’ |
|---|---|---|
| 0 | 0 | 1 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 0 |
2.16.6 NOR Gate (NOR गेट)
The NOR gate outputs the complement of the OR gate. It outputs 1 only when all inputs are 0.
NOR गेट OR गेट का पूरक आउटपुट देता है। यह तभी 1 आउटपुट देता है जब सभी इनपुट 0 हों।
- Symbol: (NOR Gate Symbol)
- Truth Table:
| Input A | Input B | Output (A + B)’ |
|---|---|---|
| 0 | 0 | 1 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 0 |
2.16.7 XNOR Gate (XNOR गेट)
The XNOR gate outputs 1 when both inputs are the same.
XNOR गेट तब 1 आउटपुट देता है जब दोनों इनपुट समान हों।
- Symbol: (XNOR Gate Symbol)
- Truth Table:
| Input A | Input B | Output (A ⊕ B)’ |
|---|---|---|
| 0 | 0 | 1 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
2.17 Applications of Logic Gates (लॉजिक गेट्स के अनुप्रयोग)
- Used in designing arithmetic circuits such as adders and subtractors
- Essential in digital circuits like multiplexers, demultiplexers, encoders, and decoders
- Used in sequential circuits like flip-flops, counters, and memory devices
- Widely applied in control systems and computer processors
Practice Questions (अभ्यास प्रश्न)
Multiple Choice Questions (MCQs)
- Which gate outputs 1 when exactly one input is 1?
(a) AND | (b) OR | (c) XOR | (d) NOR - What is the output of a NAND gate when all inputs are 1?
(a) 0 | (b) 1 | (c) -1 | (d) None - What is the complement of an OR gate?
(a) NOR | (b) NAND | (c) AND | (d) XOR - Which gate outputs 1 when both inputs are the same?
(a) XOR | (b) NAND | (c) XNOR | (d) OR - Which gate is also known as an inverter?
(a) OR | (b) NOT | (c) AND | (d) XOR - What does the truth table of a NOR gate show for all 0 inputs?
(a) 1 | (b) 0 | (c) -1 | (d) None - What is the symbol for the XOR gate operation?
(a) × | (b) + | (c) ⊕ | (d) ‘ - Which gate combines the properties of AND and NOT?
(a) NAND | (b) XOR | (c) OR | (d) NOR - What is the application of XNOR gates?
(a) Error detection | (b) Multiplexers | (c) Flip-flops | (d) All of the above - Which gate is used for equality checking?
(a) XNOR | (b) XOR | (c) NAND | (d) NOR
Answers to MCQs:
1: (c), 2: (a), 3: (a), 4: (c), 5: (b), 6: (a), 7: (c), 8: (a), 9: (d), 10: (a)
Short Answer Questions (लघु उत्तरीय प्रश्न)
- What is the main function of a XOR gate?
Answer: A XOR gate outputs 1 when exactly one input is 1. - How does a NAND gate differ from an AND gate?
Answer: A NAND gate outputs the complement of the AND gate. - Define XNOR gate with an example.
Answer: The XNOR gate outputs 1 when both inputs are the same, e.g., A = 1, B = 1 → Output = 1. - What is the purpose of a NOT gate?
Answer: A NOT gate inverts the input, turning 1 into 0 and vice versa. - State one application of a NOR gate.
Answer: NOR gates are used in universal logic circuits.
Long Answer Questions (दीर्घ उत्तरीय प्रश्न)
- Explain the functioning of NAND, NOR, XOR, and XNOR gates with truth tables and examples.
- Discuss the role of logic gates in digital circuit design with practical applications.
- How are truth tables useful for understanding and designing digital logic circuits?
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