# Resistor Puzzle—the sequel

### Resistor Puzzle—the sequel

It’s time for some fun! I’ve known a few folks who have tormented colleagues with a resistor cube—equal resistors on all sides. So in case you’ve solved that one, let’s add a twist. In this cube, not all the resistors are equal. The resistance from A to B is 1Ω. Resistor values are indicated, except for those marked “R?” in red.  What is the required value for R?

This blog marks #53, the start of a second year. It’s been great fun and a challenging gig. A week feels like three days! In the coming months, I may skip a week here and there. It will give me a chance to catch my breath… and maybe do some grandfathering, too.

I’d also like to ask for your topic suggestions. I still have a list of my own but I’d like to respond to your ideas. Of course, your suggestion could lie outside my knowledge or experience so no promises. You can post in comments below or send me an email.

And BTW… If you enjoy quizzes, here’s another, a non-technical one for your amusement.

Bruce       email:  thesignal@list.ti.com (Email for direct communications. Comments for all, below.)

• R = 3/2 ohms

• R=3 ohms

• R= 1.5ohm!

• R is 3/2 ohms

• R=3/2=1,5 Ohms

• R=3 ohms

• R ~ 8.27 Ohms

• I'm pleased that so many of you have had fun with this puzzle. (I have a tally of the number of views.) When you are sure of your answer, you can check the solution here...

e2e.ti.com/.../resistor-puzzle-solution-and-a-rant-on-schematics.aspx

• 1.5 ohms

• R=3/2 ohms

• r?=3 ohms

• Thank you, Bruce, I enjoyed it much!

My solution is R = 3/2 Ohm and also R = - 3/4 Ohm (negative value could come into account by using NICs as R); as a solutions of a quadratic eqution, obtained by repeatedly reconfiguring selected resistive wyes-to-triangles.

Some subsidiary results: for  R = 6 Ohm; the RAB = 4/3 =1.33333... Ohm and RABmax = 5/3 = 1.66666... Ohm for R = infinity (void at position of R).

• R=5/4 ohms