Question

Find the correct combination of A, B, C and D inputs which can cause the LED to glow. 

• A. 0100
• B. 1000
• C. 0011
• D. 1101

Hint:

In NOR-gate circuits, the output is HIGH only when all inputs are LOW.

Answer 1

The Correct Option is B

Step 1: Analyze the logic gates in the circuit.
The circuit consists of NOR gates at the inputs and output. The LED glows only when the final output is logic HIGH.
Step 2: Evaluate the logic condition.
For the LED to glow, the final NOR gate must receive all LOW inputs. This occurs when: \[ A=1,\; B=0,\; C=0,\; D=0 \] Step 3: Write the input combination.
\[ ABCD = 1000 \] Final Answer: \[ \boxed{1000} \]