A student wants to construct a logic circuit that behaves as a NAND gate using two switches A and B , a DC voltage source, a current-limiting resistor, and an LED. The resistor is connected in series with the voltage source to prevent short-circuiting the source. The state of a closed switch is considered as logic 1 , and the LED glowing is considered as logic 1 . Which of the following physical configurations of the

Step-by-step solution

A NAND gate outputs a logic 0 only when both of its inputs are at logic 1 . For all other input combinations, it outputs a logic 1 . In a switch-based circuit, to obtain an output of 0 when switches are closed (logic 1 ), the switches must be used to short-circuit the LED. This means the switch combination must be connected in parallel across the LED. When the switch path conducts, current bypasses the LED, turning it off. To ensure the short-circuit occurs only when both switch A AND switch B are closed, the two s