🔍 Key Concepts

• PLC internal relay (internal bit) vs a physical electro-magnetic relay coil and contacts • Meaning of normally open (NO) and normally closed (NC) contact symbols in ladder diagrams • Typical motor start/stop seal‑in circuit using a Start pushbutton, Stop pushbutton, and a holding contact

💭 Think About

• Look closely at the symbol and label for Internal relay 1. Does a PLC usually turn on a real coil inside the CPU, or does it set a memory bit that behaves like a relay in software? • Examine the drawing of Input 2 (the stop pushbutton). Is that contact shown as normally open or normally closed, and when it changes state, which device (output coil or internal relay) actually drops out to stop the motor? • Compare the contact labeled Output 1 with the contacts labeled Internal relay 1. Are they wired to real field devices or used logically to "remember" that a stop condition has been commanded?

✅ Before You Answer

• Verify whether Internal relay 1 coil is connected to any external terminals, or if it only exists inside the PLC logic (this points to physical relay vs memory bit). • Identify if Input 2 contact symbol is drawn as NC or NO; match that to the wording in the choices. • Confirm that the function of Internal relay 1 contacts is to change state in multiple rungs simultaneously when its coil/bit changes, just like a relay, but check whether this is implemented as hardware or as programmed bits in memory.