How do you read a ladder diagram showing two sensors in series versus parallel?

• A. Series implements OR logic; parallel implements AND logic.
• B. Series (in line) implements AND logic; parallel (in separate branches) implements OR logic; the coil energizes when the appropriate path is complete.
• C. Both series and parallel implement XOR logic.
• D. Ladder diagrams cannot show multiple sensors.

Answer: (B)

In ladder logic, how current can flow defines the logic. When two sensors are placed in series in the same rung, both sensors must be closed to complete the circuit, so the output coil energizes only if both are satisfied—this is AND behavior. If the sensors are placed in separate branches (in parallel), any one branch closing provides a complete path to the coil, so the coil can energize when either sensor is satisfied—this is OR behavior. The coil energizes when a complete path exists, not only when all paths are closed. The other statements don’t fit because series is not OR and parallel is not AND, and ladder diagrams can indeed show multiple sensors.