Basic Electronics: Resistors

In a follow up to a recent autopsy video, Chris and Kidwell go over several types of resistors, test out a ceramic disc heater, cover Ohm's law, and briefly touch on how these things relate to speaker setups.

[Arthur]

Those whiteboard animations are absolutely amazing. They make what you're explaining very clear.

[indoorherbivore]

Just found this channel recently, and really enjoy the video, but have to tell you that you guys really missed the unique properties of the ceramic disc elements. Yes, they are a kind of resistor, but they vary resistance with temperature. By design, these discs go to infinite resistance at around 400f. Because of this, they cannot ignite paper, and are considered "safety" heating devices. See part 2.

[sunburstbasser]

Thanks for making this. It has been a long time since I took electronics classes and this is a great introduction and refresher. How about a video on the resistor's big brother, the potentiometer?

[KeenanTims]

Yep, they're quite inductive. Definitely something to consider when using them in a circuit.

[thewii]

Love these videos, even if I already know what they're talking about.

Just wondering, could you guys do a video on current transformers? They're something I've always wanted to know about.

[engineerofestruction]

Keep them coming, especially like the animation for the white board info. Can we get a look inside the decade boxes and video on using the megger or as fluke calls them insulator checker.

[TechnoWzard]

Great video and nice whiteboard animations! Can we see the color codes and a way to memorize them next time? And just maybe explain how when a wire is coiled to make a resistor it has inductance and self-capacitance and all the electrical properties that devices made for a specific purpose end up having anyways?

[ChaoticGoodChris]

Yes but it's much better than the alternative. They used to love each other and we couldn't get any work out of them in between the constant making out.

[clony]

can you do a video on the big power supply? maybe do an autopsy but like on stuff you want to keep, kinda similar to the air raid siren autopsy.

[Monkeh]

Actually, Paul's description of the resistance test on an autoranging digital meter is accurate. See, for example, page 26 of the Fortune FS9922-DMM4 datasheet. Also see page 5 of the Thurlby 1503/1504 service manual, where you'll see the same method used on a manual ranging bench meter.

[frollard]

A speaker is simply a long length of wire all coiled up. A coiled wire with a current through it is an electro-magnet. This coil interacts with a magetic field from a known magnet on the speaker, causing the coil to move. Vary the signal (current) and you vary how the speaker moves, bingo, sound!
The reason they have different ohm impedence ratings is because a length of wire is not zero resistance - it varies depending on the characteristics of the wire like length and gauge.

[kuhrd]

In school I was always taught that "I" in the Ohm's Law and Power Law equations stood for "Induced Current".

[kiwifrogg]

The megger tester is a insulation tester, because the peek value of mains supply can exceed 320v( for a ac230v rms supply) one needs to check the break down potential of the insulation. So the NZ rules require a no more that 1meg breakdown to ground at 500v hence the high voltage output of that meter(not sure of the us rules). So you would bridge phase and neutral with the ground probe and test exposed grounds with the other probe. And some of those meters bite so watch out.

[frollard]

you can approximate because AC volts are expressed in RMS 'dc equivalent' and for boring non-inductive loads it works out the same.

[KeenanTims]

The ohmmeter is much simpler than that. It's just a precise constant current source, with the voltage across the DUT measured by the voltmeter. Ohms law then works directly and you only need one measurement.

[wuverul]

You tried going without a speaker question, but your short section on speakers in here brought up another question XD It's still a short question, though. How does a speaker actually use this resistance in operation?

[Sdnaurs]

Actually there could be a different symbol other than the R in 4R000, in some european systems a 4K resistor is expressed as 4K000 or something similar.

[MrSoundshark]

The reason they use for e.g 3R4 ohm when marking the resistors Is because on schematics the . would often be rubbed off or lost in bad copies over time :)

[Evanator]

I know a way to remember the color code but its not exactly appropriate... but you definitely wont forget it!

[redfire]

Doesn't the heater work on AC? Is it ok to approximate with the DC formulas?