Question

A bulb in the staircase has two switches, one switch is at the ground floor and the other one is at the first floor. The bulb can be turned ON and also can be turned OFF by any of the switches irrespective of the state of the other switch. The logic of the switching of the bulb resembles:

• A. XOR Gate
• B. AND Gate
• C. OR Gate
• D. XNOR Gate

Hint:

The XOR gate produces a true (1) output when an odd number of inputs are true (ON). This matches the behavior of the described switches.

Answer 1

The Correct Option is A

Step 1: Understand the behavior of the switches.
The bulb can be turned ON or OFF by either switch, regardless of the position of the other switch. This means the output (bulb's state) changes whenever any of the switches is toggled. This behavior is characteristic of the XOR (exclusive OR) gate. In an XOR gate, the output is 1 (ON) when the number of 1's (high signals) is odd. In the context of the two switches, this means that the bulb is ON when the switches are in different states (one ON and the other OFF) and OFF when both switches are in the same state (either both ON or both OFF).

Step 2: Analyze the options.
- (a) XOR Gate: Correct. This gate works like the described switches, where the output changes when the switches are in different states.
- (b) AND Gate: Incorrect. The AND gate would require both switches to be ON to turn the bulb on, which is not the case here.
- (c) OR Gate: Incorrect. The OR gate would turn the bulb ON if either switch is ON, which doesn't match the given behavior.
- (d) XNOR Gate: Incorrect. The XNOR gate works oppositely to the XOR gate, as it would require both switches to be in the same state to turn the bulb ON.

Step 3: Conclusion.
Thus, the correct answer is (a) XOR Gate.