What do you mean by a logic gate, a truth table and a Boolean expression?

Question

Accepted Answer

A LOGIC GATE is a digital circuit having one or more input signals but only ONE output signal, in which the output state (high/1 or low/0) at any moment is fixed by a definite logical relationship to the states currently present at its inputs -- it is, in effect, a switching circuit that controls the flow of a signal according to that rule, which is why such circuits are called 'gates'. A TRUTH TABLE is the most direct and complete way of specifying a logic gate's behaviour: it is simply a table listing EVERY possible combination of input states (for a two-input gate, the four combinations 00, 01, 10, 11) alongside the corresponding output the gate produces for each combination -- since a truth table lists every case explicitly, it leaves nothing about the gate's function ambiguous. A BOOLEAN EXPRESSION is a short mathematical (algebraic) statement, using the operations of Boolean algebra (AND, written $\cdot$ ; OR, written $+$ ; NOT, written with an overline), that expresses the exact same input-output relationship as the truth table, but in compact symbolic form rather than as an exhaustive list -- for instance $Y=A\cdot B$ for an AND gate is fully equivalent to (and derivable from, or used to …

Start your 14-day free trial to unlock the full solution →

Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

CBSE 2025Set ANNUAL1 markMCQ
$Q. The gate which produces high output, when its both inputs are high is -$
(a) X-OR gate
(b) AND gate
(c) NAND gate
(d) NOR gate
›Reveal solutionSolution

An AND gate's truth table gives a high (1) output only when every input is high.

For a two-input logic gate with inputs A, B: the AND gate follows $Y = A\cdot B$ , so $Y=1$ only when $A=1$ and $B=1$ (both inputs high); for any other input combination $Y=0$ . The OR-family and NAND/NOR gates behave differently — a NAND gate is high for every combination except both-high, and a NO …

Start your 14-day free trial to see the full solution →
CBSE 2021Set A1 markMCQ
$Q. Which of the following is correct for fundamental gate? (A) AND, OR, NOT (B) AND,$
(OR)
$(C) NAND, NOR (D) OR, NOT$
›Reveal solutionSolution
The three fundamental logic gates are AND, OR and NOT.

Logic gates are the building blocks of digital circuits. The three fundamental (basic) gates are:

OR — output 1 if any input is 1 (logical addition, A+B),

AND — output 1 only if all inputs are 1 (logical multiplication, A·B),

NOT — inverts the input (Ā). …
Start your 14-day free trial to see the full solution →
CBSE 2019Set ANNUAL1 mark
$Q. Mention one practical application of logic gates.$
›Reveal solutionSolution

Logic gates implement binary decision-making, so they form the core of every digital device, from calculators to computers to automated control systems.

Application

Logic gates (AND, OR, NOT, NAND, NOR, XOR) combine binary (0/1, HIGH/LOW) inputs according to Boolean rules. A practical example: in a digital calculator or computer, arithmetic and logical operations are built up entirely from networks of logic gates; another example is an automatic control circuit (e.g. a security/alarm system) that switches on an output only when a specific combination of input conditions ("sensor triggered" AND "system armed") is satisfied.

§ Honest curriculum note

…

Start your 14-day free trial to see the full solution →
CBSE 2019Set ANNUAL1 mark
$Q. Name the logic gate which generates high output when at least one input is high.$
›Reveal solutionSolution

The logic gate that gives a high output if any one (or more) input is high is the OR gate.

…

Start your 14-day free trial to see the full solution →

Q.What do you mean by a logic gate, a truth table and a Boolean expression?

Concept understanding — Logic Gates — NOT, OR and AND Gates

Q.What do you mean by a logic gate, a truth table and a Boolean expression?

🎓Unlock everything free for 14 days

Unlock everything free for 14 days