Can anyone help me how to come up with this question's solution?


A rotary potentiometer consists of a fine wire wound on a circular former, whose inner diameter is 2.5 cm. The resolution in degrees is 0.176. Calculate the maximum number of turns that can be wound on the former per cm.

Answer: 260

My solution:

My Solution

  • 3
    \$\begingroup\$ You may appear Lame without the effort of showing attempts \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Oct 18 '20 at 13:57
  • \$\begingroup\$ Expert question, what % is the practical minimum non-zero resistance _/ \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Oct 18 '20 at 13:58

Understanding the physical form of a wirewound potentiometer may help you comprehend the question. This photo is actually a winding on a ferrite core (not a potentiometer), but the form of winding is the same:
this is a ferrite core, not a potentiometer.
Image from http://www.jumaradio.com/juma-tx500/tx500-toroidal-coils.html


enter image description here

Figure 1. A wirewound 50 W potentiometer. Image source: Google image search links to surf.hr but the link is dead.

Notice that the wire is insulated except where the wiper is to contact it. Also note the relevance of the inner diameter specification. The wire is spaced further apart on the outer diameter.

The answer given is correct. Can you work it out?

The question states, "The resolution in degrees is 0.176." Your first calculation is incorrect.

  • \$\begingroup\$ I tried but i could not get the answer \$\endgroup\$ – Techilluminati Oct 18 '20 at 15:23
  • \$\begingroup\$ Please edit your question to show what you tried. It's simply maths. There is no electrical knowledge required. \$\endgroup\$ – Transistor Oct 18 '20 at 15:27
  • \$\begingroup\$ See the update. \$\endgroup\$ – Transistor Oct 19 '20 at 17:51

You have calculated the number of turns per degree. You have been asked for the number of turns per centimeter.

You need to take into account the circumference of the circular former to work out the correct answer.


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