421
Virgin Physicists (lemmy.world)
all 38 comments
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[-] NocturnalMorning@lemmy.world 65 points 2 years ago

First of all, why are they in the chip aisle looking for resistors? Everybody knows they're in the bread aisle...

[-] Tolookah@discuss.tchncs.de 33 points 2 years ago

If you're breadboarding this, you've already lost

[-] Routhinator@startrek.website 12 points 2 years ago

He's going to make potato chip resistors to get the right number of course.

[-] Blum0108@lemmy.world 6 points 2 years ago
[-] SkybreakerEngineer@lemmy.world 3 points 2 years ago

Careful, capacitors reduce ripples

[-] yucandu@lemmy.world 29 points 2 years ago* (last edited 2 years ago)

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.

[-] SupaTuba@lemm.ee 11 points 2 years ago

I admire it but also...wtf lol

[-] xthexder@l.sw0.com 3 points 2 years ago

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.

[-] RogueBanana@lemmy.zip 3 points 2 years ago

That's cool, could you share some photos? The theramin I mean

[-] JohnDClay@sh.itjust.works 27 points 2 years ago

There is if you have a potentiometer and a steady enough hand!

[-] muntedcrocodile@lemm.ee 18 points 2 years ago

U probably need a climate controlled box as well.

[-] SaharaMaleikuhm@feddit.org 3 points 2 years ago

Can you even measure that accurately? Like is it physically possible?

[-] xthexder@l.sw0.com 4 points 2 years ago* (last edited 2 years ago)

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.

[-] Adalast@lemmy.world 1 points 2 years ago

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.

[-] anomnom@sh.itjust.works 2 points 2 years ago

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.

[-] Adalast@lemmy.world 1 points 2 years ago

Lol, I was actually going to add that but decided it would be too pedantic if I said it myself.

[-] Zagorath@aussie.zone 27 points 2 years ago

What's the significance of that number? It's less than 0.1 away from tau, but somehow I doubt that's it...

[-] AlbinoPython@lemmy.world 1 points 2 years ago

I can't be arsed to check but I think it's 2 pi which is useful when dealing with sine waves.

[-] Zagorath@aussie.zone 0 points 2 years ago

2 pi is tau, which is what I said it's less than 0.1 away from, but still not equal to.

[-] TangledHyphae@lemmy.world 2 points 2 years ago
[-] Zagorath@aussie.zone 1 points 2 years ago

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.

[-] TangledHyphae@lemmy.world 2 points 2 years ago

That's a fantastic video. I follow Numberphile but never saw this one, thanks for sharing.

[-] skisnow@lemmy.ca 23 points 2 years ago

Simple, all you need is a 6 ohm resistor and a 0.18457216 ohm resistor in series.

[-] Spacehooks@reddthat.com 3 points 2 years ago

No just get a bunch in parallel!

[-] A_A@lemmy.world 18 points 2 years ago* (last edited 2 years ago)

Fixed resistors
https://en.m.wikipedia.org/wiki/Resistor
The TCR of foil resistors is extremely low, and has been further improved over the years. One range of ultra-precision foil resistors offers a TCR of 0.14 ppm/°C, tolerance ±0.005%, long-term stability (1 year) 25 ppm, (3 years) 50 ppm (further improved 5-fold by hermetic sealing), stability under load (2000 hours) 0.03%, thermal EMF 0.1 μV/°C, noise −42 dB, voltage coefficient 0.1 ppm/V, inductance 0.08 μH, capacitance 0.5 pF.

Quantum based resistors :
https://en.m.wikipedia.org/wiki/Quantum_Hall_effect
Quantum Hall effect →
Applications →
Electrical resistance standards :

(...) Later, the 2019 revision of the SI fixed exact values of h and e, resulting in an exact
R~K~ = h/e^2^ = 25812.80745... Ω.

(this is precise to at least 10 significant digits)

Quantum Ampere Standard
https://www.nist.gov/noac/technology/current-and-voltage/quantum-ampere-standard
.
https://www.nist.gov/noac/technology/current-and-voltage

(...) Quantum-based measurements for voltage and current are moving toward greater miniaturization (...)

(there also been research for defining a quantum based volt standard)

[-] Naich@lemmings.world 12 points 2 years ago

A 6.2R in parallel with a 2.5K is pretty close.

[-] Tolookah@discuss.tchncs.de 9 points 2 years ago

Add in a 400k and you're better than most tolerances you can find

[-] friendly_ghost@beehaw.org 5 points 2 years ago

And no spherical cows either??

[-] murd0x@lemmy.ml 4 points 2 years ago
[-] Spacehooks@reddthat.com 3 points 2 years ago

Love how there are so many actual solutions in The comments

[-] frezik@midwest.social 4 points 2 years ago

But not really. At this level of precision, the heat from electricity passing through it would throw off the actual resistance value.

[-] realitista@lemm.ee 3 points 2 years ago

Bet they're all engineers.

[-] TangledHyphae@lemmy.world 2 points 2 years ago

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.

[-] Corno@lemm.ee 1 points 2 years ago

That's revolting.

this post was submitted on 31 Mar 2025
421 points (97.9% liked)

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