Two or more normally closed switches wired in series describe which logic element?

• A. AND
• B. NOR
• C. OR
• D. NAND

Answer: (B)

Normally closed switches carry current by default and open when their control is energized. When you wire two NC contacts in series, the current can flow only if both contacts remain closed. Each contact will open if its associated control signal goes high, so if either control is energized, the circuit breaks and the current stops.

So the path is completed only when both inputs are false (not energized). That means the output is true only when all inputs are false, which is the NOR behavior. If any input is energized, the path opens and the output goes false.

In short, two normally closed switches in series implement the NOR function because the circuit conducts only when all inputs are inactive.