What distinguishes a sinking circuit from a sourcing circuit in industrial control?

• A. A sinking circuit provides a ground return path for the load; a sourcing circuit provides a positive supply to the load.
• B. A sinking circuit provides a positive supply; a sourcing circuit provides ground.
• C. Sinking circuits are used with AC only; sourcing with DC only.
• D. Sinking means the load is on the negative terminal; sourcing on the positive terminal.

Answer: (A)

Understanding this distinction comes from looking at current flow and where the return path goes. A sinking circuit uses the control device to complete the circuit by pulling current down to ground; the load is connected to the positive supply, and when the device activates, current flows from that positive supply, through the load, and into the sinking element to ground. A sourcing circuit, by contrast, provides current from the positive supply to the load, with the return path going through the control or ground as the load completes the circuit.

So the statement that sits best matches this idea: sinking provides a ground return path for the load, while sourcing provides a positive supply to the load.

The other options mix up the direction of current flow or oversimplify the setup (AC vs DC limitations, or tying sinking/sourcing strictly to specific terminals), which doesn’t align with how these outputs actually behave in most industrial control configurations.