cross-posted from: https://lemmy.world/post/27589038
Lol this one was great, thanks for sharing. My partner teaches physics and I do EE on the side, I like rubbing these in her face sometimes.
this post was submitted on 31 Mar 2025
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That's revolting.
Love how there are so many actual solutions in The comments
Bet they're all engineers.
But not really. At this level of precision, the heat from electricity passing through it would throw off the actual resistance value.
Ohm no !
This implies a physicist would do anything practical ever
Simple, all you need is a 6 ohm resistor and a 0.18457216 ohm resistor in series.
No just get a bunch in parallel!
And no spherical cows either??
A 11.8 and a 13 in parallel is 6.1854838709677 which is 0.01% off from that resistance. Of course even using matched 1% would screw you as soon as someone opens the door.
You could get exactly 6.1854838709677 for an instantaneous moment by heating up a 6ohm resistor.
So you just need to figure out the precise amount of prewarming, then subsequently cooling in coordination with the circuit's load to make sure it stays at the right temperature?
just now realizing that I missed this comm actually
I used to make shunt resistors out of a pencil and a piece of paper. Rub pencil all over paper, cut strips to size of required resistance.
EDIT: I mean megaohm resistors not shunt resistors. 20MOhm for DIY theramin.
That's cool, could you share some photos? The theramin I mean
This is exactly how high precision resistors are calibrated. A laser is usually used to notch out bits of the resistor to tune it after it's made.
I made a potentiometer with paper and graphite clay once
Confuses me that anybody would downvote you for this. I've made makeshift capacitors out of rolled aluminum foil. It's dumb, but it worked for what I wanted (triggering a trackpad via stepper motors for testing microcontroller code.) Plus I just wanted to see if it even worked. Life = science experiments.
I admire it but also...wtf lol
A 6.2R in parallel with a 2.5K is pretty close.
Add in a 400k and you're better than most tolerances you can find
First of all, why are they in the chip aisle looking for resistors? Everybody knows they're in the bread aisle...
He's going to make potato chip resistors to get the right number of course.
Just count the ripples!
Careful, capacitors reduce ripples
If you're breadboarding this, you've already lost
What's the significance of that number? It's less than 0.1 away from tau, but somehow I doubt that's it...
I can't be arsed to check but I think it's 2 pi which is useful when dealing with sine waves.
2 pi is tau, which is what I said it's less than 0.1 away from, but still not equal to.
For me, it was this video. It came out shortly after I graduated high school, and though I was pretty good at maths, I struggled to really conceptualise the fundamental intuition behind trigonometric functions and the (polar) complex plane. Instead, I was relying on brute memorisation of the unit triangles. Learning about tau and how it relates just instantly caused everything to click with me.
I assumed the number is not significant, figure it's just supposed to mock the idea that physicists don't know what tolerances are.
An experimental physicist should know as far as I know meanwhile a real (theoretical) physicist would probably not even touch numbers that have those scary decimals.
There is if you have a potentiometer and a steady enough hand!
Can you even measure that accurately? Like is it physically possible?
Based on some rough calculations... no. A precision of 0.0000000000001 ohms is 1000x less than the resistance of 1um of copper with a diameter of 1cm (A piece of wire 10,000x wider than it is long). I'm sure a few molecules of air between your contact points would cause more noise in the measurement.
I thought it had to do with physicists working off theoretical calculations finding precise values for the circuit and not realizing that components come in discrete values.
Yeah, but they could just calculate the right mix of parallel and series discrete resistors to get there.
It’s gonna make a long BOM though.
Lol, I was actually going to add that but decided it would be too pedantic if I said it myself.
U probably need a climate controlled box as well.
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