You are given a "black box" with something inside. You donotknow what I put inside that box, it's sealed.
You have to find out--as much as you can--what is inside.
For this I give you two hints:
1.Two wires are coming out of that box. These wires are connectedinsome way with what is inside. So the only thing you can do istomake measurements at those wires, or plug twose two wires inallsort of electrcal diagrams, to try to find out what do theydoinside, where do they go inside.
2. You know that inside the box, and connected to these2outgoing wires, you have only DC components. Like: resistors,otherwires, DC batteries, solenoides, and instruments ofmeasurement,all interconnected inside in a way you don't know, andyou need tofind.