🔍 Key Concepts

• PLC input vs output addresses (IN-0, IN-1, OUT-0, OUT-1) and how they relate to SW-0, SW-1, Lamp 0, Lamp 1 • How series contacts and parallel branches in a ladder diagram affect when an output coil is energized • The effect of SW-0 closed and SW-1 open on the logic paths feeding OUT-0 (Lamp 0) and OUT-1 (Lamp 1)

💭 Think About

• Trace the current path for Lamp 0: with SW-0 closed and SW-1 open, does the series path of IN-0 and IN-1 to OUT-0 stay complete or become open? • Look at the second rung feeding Lamp 1: with SW-0 closed, what happens to IN-0 and OUT-0, and does that create a path to energize OUT-1? • Compare which rungs are in series and which are in parallel to decide whether each lamp sees a closed circuit or an open circuit under the given switch positions.

✅ Before You Answer

• Verify which PLC input terminal each switch is wired to and which output terminal each lamp is wired to (SW-0→IN-0, SW-1→IN-1, Lamp 0→OUT-0, Lamp 1→OUT-1). • Confirm that Lamp 0’s coil (OUT-0) requires both IN-0 and IN-1 to be true at the same time, while Lamp 1’s coil (OUT-1) depends on IN-0 and the state of OUT-0. • Double‑check whether OUT-0 being de‑energized or energized will open or close the contact labeled OUT-0 in the second rung, and how that affects Lamp 1.