Define ladder logic rung and its components.

• A. Motors and valves
• B. Inputs (contacts), outputs (coils), and memory
• C. Sensors and actuators only
• D. Resistors and capacitors

Answer: (B)

In ladder logic, a rung is a single horizontal logic element that energizes an output when the conditions on its left are true. The essential parts on a rung are input conditions shown as contacts (normally open or normally closed), the output shown as a coil (which drives an actuator), and memory elements (internal memory bits or relays) that can store state for later use. Inputs represent sensors or switches; outputs represent the devices you want to operate; memory allows latching or maintaining state so the program can remember something across cycles or create sequences. This is why the correct answer includes inputs, outputs, and memory. Motors and valves describe actuators you might control but don’t define the rung itself; sensors and actuators alone miss the memory aspect; resistors and capacitors aren’t part of the ladder logic rung construct.