Question

The output of an 'OR' gate is 'one'

• A. if both inputs are zero
• B. if either or both inputs are '1'
• C. if only both inputs are '1'
• D. if either input is zero

Hint:

An 'OR' gate represents logical addition ($A + B = Y$). As long as there is a '1' anywhere in the inputs, the sum will be treated as high ('1'). The only way to get a '0' is if all inputs are '0'.

Answer 1

The Correct Option is B

Step 1: Recall what an OR gate does.
An OR gate gives output $1$ if at least one input is $1$. It gives $0$ only when every input is $0$.

Step 2: Write the truth table.
For inputs A and B and output Y:
A=0, B=0 gives Y=0.
A=0, B=1 gives Y=1.
A=1, B=0 gives Y=1.
A=1, B=1 gives Y=1.

Step 3: Look at the rows that give 1.
The output is $1$ in three rows: when only B is $1$, when only A is $1$, and when both are $1$.

Step 4: Describe the pattern.
In all three of those rows, at least one input is $1$. That is the simple rule for an OR gate.

Step 5: Look at the row that gives 0.
The output is $0$ only when both inputs are $0$. So that case is the opposite of what we want.

Step 6: Match the wording of options.
The phrase "either or both inputs are $1$" exactly describes "at least one input is $1$".

Step 7: State the result.
The output is $1$ if either or both inputs are $1$, which is option (2).
\[ \boxed{\text{if either or both inputs are } 1} \]