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I came across this description of a rheostat along with a diagram:

enter image description here

...The best example is the traditional dial controlling volume on a radio. The outer ring, or toroid coil, consists of a resistive wire wrapped in a spiral about a ring of insulating material. Electricity must travel along a sliding wiper and through the coil before itleaves the resistor. When the knob is turned clockwise, the electricity has less wire to travel through so that the resulting current is stronger and the volume is louder.

Won't turning the knob clockwise increase the distance between input and output, causing the electricity to have to travel through more resistive wire, thus increasing resistance, decreasing amperage and consequently, volume?

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    \$\begingroup\$ A volume control is invariably a potentiometer, not a rheostat. Connect signal to the "not used" terminal and ground to the"current in" terminal. Now you get the right variable voltage from the wiper. \$\endgroup\$
    – user16324
    Commented Jun 29, 2021 at 11:55

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Yes you are correct, the drawing appears to be mirrored. However, note that wire wound pots are rarely used these days. Instead carbon or conductive plastic potentiometers are typical, which use the same principal. Wire wound pots are usually often used when high current/power rating or low resistance is needed.

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    \$\begingroup\$ Thanks but was aware of that. Was getting a refresher, this jumped out, so wanted to double check that I wasn't rusty to the point of missing something obvious. \$\endgroup\$
    – puwlah
    Commented Jun 29, 2021 at 7:09
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    \$\begingroup\$ Rheostats are still used on "100V line" PA (public-address) systems. I'm standing beside one right now. The rheostat is simply wired in series with the loudspeaker transformer (which usually has multiple power tap-off points on the secondary). It's not hi-fi but it works. \$\endgroup\$
    – Transistor
    Commented Jun 29, 2021 at 8:44
  • \$\begingroup\$ @Transistor that's true! (back in the 90's I designed such a system with well over 1000 panels.) They can sound pretty good with decent speakers and transformers. It's a fairly specialist application though. \$\endgroup\$
    – danmcb
    Commented Jun 29, 2021 at 8:52
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    \$\begingroup\$ The difference between a rheostat and a potentiometer is that the rheostat is a two terminal variable resistance (controls current) whereas a potentiometer is a three terminal device which varies the voltage (potential) at the centre terminal. \$\endgroup\$
    – Ian Bland
    Commented Jun 29, 2021 at 8:53
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    \$\begingroup\$ @IanBland - you are correct, thank you. Will correct. \$\endgroup\$
    – danmcb
    Commented Jun 29, 2021 at 9:02

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