How are switches wired to create an OR logic circuit?

• A. Two normally closed switches in series
• B. Two normally open switches in parallel
• C. One normally closed in parallel
• D. Two normally open in series

Answer: (B)

To realize an OR function with switches, use parallel paths that are normally open. If either path is completed, the output turns on. With two normally open switches wired in parallel, there are two independent routes from power to the output. When either switch is pressed, it closes its path and the output activates. If neither is pressed, both paths stay open and the output stays off. This matches OR behavior: the output is on if at least one input is on.

The other configurations don’t produce OR. Two normally closed switches in series would be on by default and only turn off when a switch is pressed, which behaves differently (more like a default-on control, not OR). A single normally closed switch in parallel would also be on by default, turning off only when actuated. Two normally open switches in series require both to be closed to complete the circuit, which corresponds to an AND function, not OR.