🔍 Key Concepts

• Figure B shows the schematic for a variable resistor (rheostat), not a plain fixed resistor or a full three‑terminal potentiometer. • Count how many electrical terminals are shown in the symbol (labeled 1 and 2) and compare that to how many lugs or studs appear on each physical resistor option. • Look for some kind of adjustment mechanism (shaft, screw, knob, or slider) on the resistor illustrations that would allow its value to be changed.

💭 Think About

• Which of the pictured resistors clearly has an adjustment control but is normally used with only two connections rather than three? • Among figures 4, 6, 10, and 11, which ones appear to be fixed power resistors (no moving parts), and which ones appear to be adjustable? Narrow it down to the adjustable ones first. • Once you’ve identified the adjustable resistors, ask yourself: which one best represents a variable resistor used in series (rheostat) rather than a small signal control potentiometer?

✅ Before You Answer

• Verify that the figure you choose has visible moving/adjustable parts (knob, wiper, or slider). • Verify that the device can logically be wired with two external terminals, matching the two connection points in symbol B. • Double‑check that you are not picking a fixed resistor (no adjustment mechanism) or a three‑terminal potentiometer symbol like the one shown in figure C.