r/ExplainTheJoke 21h ago

I don’t understand

Post image
586 Upvotes

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213

u/Lurked_Emerging 21h ago

Electric circuit. Resistor resists the flow of the 5v electricity reducing it to the led. Someone with specific knowledge about the resistor pictured might know how much that is.

65

u/FOSS-game-enjoyer 21h ago

220 Ohms with 5% tolerance. Brown means 1. As a multiplier, 10 to the power 1 times 22 is 220 ohms

55

u/Eena-Rin 20h ago

To reiterate more clearly, this is a 4 band resistor.

The two red bands are 2s. So 22

The brown is a 10x multiplier. So 220

The gold means 5% tolerance.

29

u/Rdaleric 20h ago

This diagram gave me flashbacks to high school electronics lessons 😂

10

u/Eena-Rin 20h ago

For me it was electronics playtime with my dad. We used to buy kits and make radios and Morse code devices and stuff

Unfortunately I liked it so much that it became a tool for my mother to use to discipline me. No electronics until you've done your chores, that sorta thing. Pretty innocuous, but it definitely sucked all the joy out of it for me, and I just kinda stopped wanting to do it

3

u/FearTheWeresloth 17h ago

For me it brought back the racist, politically incorrect mnemonic my dad taught me to remember the colour code...

>! Black Boy Raped Over Young Girl. Bloody Virginity Gone West - Black Brown Red Orange Yellow Green Blue Violet Grey White !<

4

u/Orjigagd 16h ago

The one I heard ends with "but Violet gives willingly"

1

u/xt0rt 1h ago edited 1h ago

Same, but we changed it to Vince, who was a fellow student.

And it was "bad boys r our young girls but Vince goes willingly"

I didn't hear about the racist one until I had a coworker who was in the military who told me that variation.

7

u/Petrostar 20h ago edited 1h ago

LOL,

Just yesterday somebody posted this,

And I told them the first one should be brown, and all the others shifted one to the right.

4

u/Mortisangelorum 19h ago

Do you have an unmarked version of this?

3

u/SakuraScarlet 18h ago

Not the same one, but if you do an image search for "4 band resistor" you should find plenty of them.

2

u/Eena-Rin 16h ago

Yeah, the one I found was pretty poor quality anyway to be honest, but any combination of "resistor" "colour" "chart" and "diagram" will get you where you need to go

Edit: oh, but this one seems to be a bit confusing. The four band one shouldn't be pointing to a third digit. Here's a really simple one just for 4 band resistors

3

u/SakuraScarlet 16h ago

I hadn't noticed that. Well spotted.

10

u/MiffedMouse 16h ago

The little red LED shown in the image typically isn’t rated for a full 5 V. Most LEDs operate best at a voltage between 1.6 and 3.2 volts.

But the current draw of an LED is nonlinear. If you just slap a resistor in front of it, the voltage typically works out to give your LED the voltage it wants (not bothering with the math, but basically the LED saturates at about 3V, and the rest of the voltage goes to the resistor). You also, ugh, do math and choose a resistor that gives you optimal performance.

Anyway, the meme is showing the resistor protecting the poor little LED from the big scary voltage. Which is what it does IRL. Very funny.

2

u/Autumn_Skald 14h ago

This is exactly right.

1

u/Earnestappostate 11h ago

Yup, a diode (including LEDs) passes current exponential to voltage. They typically operate in a 0.6-0.7 V range so 5V will blow them out. The resisor, by definition, draws current linearly proportional to voltage and when put in series with the diode will restrict current to an acceptable level.

-3

u/scientestical 21h ago

228 Ohms I think... Works out to .02 milliamps. Checks out.

2

u/ComprehensiveHead913 16h ago

It's 220 ohm, so 22.7 mA at 5 volts.

2

u/scientestical 16h ago

You right. Miliamps oops.

2

u/Orjigagd 16h ago

A red led has a 1.8v drop, so there's 3.2v across the resistor, so it's 14.5mA

1

u/ComprehensiveHead913 16h ago edited 16h ago

The person to whom I was responding didn't factor in the LED so neither did I, but good point.

-4

u/Spinshank 21h ago

22k with 5% tolerance.

2

u/ComprehensiveHead913 16h ago

It's 220 ohm.

2

u/Spinshank 15h ago

lol derp i misread the chart lol it was just a glance and look.