NOT logic is formed by __________.

• A. One normally closed switch
• B. Two normally open switches
• C. A resistor
• D. A capacitor

Answer: (A)

Inversion of a signal is achieved by a normally closed switch. When the control input is inactive, the normally closed contact is closed, allowing current to flow and producing a high output. When the input is activated, the switch opens, breaking the circuit and producing a low output. This direct on/off inversion matches the NOT operation.

The other options don’t provide a true NOT behavior by themselves: a resistor simply limits current and doesn’t switch states; a capacitor stores charge for timing or filtering but doesn’t invert a logic level on demand; two normally open switches require both to close to conduct and don’t automatically invert a single input.