Question

Which gate corresponds to the action of parallel switches?
(A) NAND gate
(B) NOR gate
(C) OR gate
(D) AND gate

Answer 1

Hint:
The parallel switches are used to control the bulb or other electrical instruments by two switches, when the two switches are in opposite directions then the bulb or electrical instruments will operate. By using the logic gates also, the action of the parallel switch should be done.

Complete step by step solution:
Let us assume that the two switches are $A$ and $B$ , and also assume that $0$ is the bulb off condition and also the switch off condition and $1$ is the bulb on condition and the switch on condition.
The condition for the parallel switches is when the two switches are in on condition, the bulb will not operate and when the two switches are in off condition, the bulb will not operate. So, in parallel switch condition, the two switches are in opposite, like one switch is in on condition and the other switch is in off condition, then only the bulb will operate.
Condition for parallel switch:

Switch $A$	Switch $B$	Output
$0$	$0$	$0$
$0$	$1$	$1$
$1$	$0$	$1$
$1$	$1$	$0$

The above table shows the correct condition of the working of the parallel switches, when the $0$ indicates off condition and $1$ indicates on condition.
Now using the logic gates condition which are given in the option, then
NAND gate:

Switch $A$	Switch $B$	Output
$0$	$0$	$1$
$0$	$1$	$1$
$1$	$0$	$1$
$1$	$1$	$0$

The NAND gate will not exactly match with the parallel switch condition.
NOR gate:

Switch $A$	Switch $B$	Output
$0$	$0$	$1$
$0$	$1$	$0$
$1$	$0$	$0$
$1$	$1$	$0$

The NOR gate will not exactly match with the parallel switch condition.
OR gate:

Switch $A$	Switch $B$	Output
$0$	$0$	$0$
$0$	$1$	$1$
$1$	$0$	$1$
$1$	$1$	$1$

The OR gate will not exactly match with the parallel switch condition.
AND gate:

Switch $A$	Switch $B$	Output
$0$	$0$	$0$
$0$	$1$	$0$
$1$	$0$	$0$
$1$	$1$	$1$

The AND gate will not exactly match with the parallel switch condition.
So, the options which are given in the question will not be used to do the action of the parallel switches.

Note:
The logic gate operations must be known to solve this problem, the AND gate is the multiplication of the two input values, OR gate is the sum of the two input values, NAND gate is the opposite of the output of the AND gate, NOR gate is the opposite of the output of the OR gate.