Im talking about the average guy/girl buying a bag of resistors off ebay for their Arduino/RasPi projects. Not the electrical engineer who needs a .5% Vishay 220K 1000V wirewrapped precision restor for their pulsed ruby laser.

Resistor do have a voltage breakdown specification. Using pulsed current, it would be possible to meet the resistors power ratings while exceeding its breakdown voltage rating. Consider what would happen if an EHT spark current is applied to a resistor, depending on its structure and its resistance, an electric arc may flash across the resistor material that is usually coiled around the ceramic body of the resistor. A failure of a resistor by this mode is sometimes indicated by the black track marks left by the arc in the resistor insulating passivation coating. This is in contrast to the brown burn discolouration often left on a resistor whose power rating has been exceeded. The resistor break down rating is of notable importance in high voltage multiple circuits or those used to monitor a high voltage.

As has already been said in comments. The voltage rating of a resistor depends on the insulation encapsulating the resistor. You may not drop a very high voltage across the resistor, but it can still be at a potential of 100's of volts, as in high value discharge resistors in capacitive voltage droppers, with respect to other components on the PCB. If it is a carbon film, the voltage developed between the edges of the etched spiral inside the resistor become a factor. Also if you drop too high a voltage across ends the resistor then you will get an arc over the surface of the resistor. This is important in DMMs where resistors are used at very low current to drop 100's of volts for the electronic circuitry to measure. To solve this problem they use a chain of resistors in a line to drop the voltage progressively. This is why SMD type resistors are of special concern.

@TheEmbeddedHobbyist

4 жыл бұрын

well stated, if your into 100's of volts or safety it's best to put a few in series for protection.

Hello, I discovered your channel a couple weeks ago and wanted to thank you for providing this amazing content for free. I've always been interested in electronics but couldn't keep up with the complex explanations online. Your videos are easy to understand, yet not oversimplified. Thank you! :)

If you have a high crest factor signal where the rms value of the voltage is much lower than the peak value, it is possible to have an arc over even though the max dissipation is within limits. Another situation is for very high value resistors where the voltage across it can be very high before the max dissipation is reached.

Metal tape on cardboard? I had an EE class where that was part of an exam. Each person got a homemade capacitor like that, then based on the areas of the plates, and the dielectric material, we had to estimate the capacitance. Not too hard, if you were ready for it.

The simple wattage rating of resistors is more about heat tolerance and dissipation than voltage or current. Put a heatsink on a resistor and it can tolerate a higher wattage and therefore a higher DC or RMS AC voltage. I don't think any of the comments so far mention pulsed waveforms. A resistor can tolerate a much higher peak voltage with a 0.1% duty cycle waveform (depending on frequency) than DC. As mentioned previously in the comments, a resistor can arc. They are also imperfect and have unintentional capacitance and inductance. So resistors have an absolute max peak voltage rating as well as an absolute max frequency rating (based on material and distance between connections - like SMDs as previously mentioned). We as hobbyists tend to ignore these ratings since we rarely approach them. Those of us that can generate a 2000v picosecond pulse across a 10 ohm resistor should already be aware of such limits. If not, well ... protective eye-ware is mandatory.

@trelligan42

4 жыл бұрын

Darn, I was going to say this. Also the formula was a bit misused. Good video, though it might have been better with a couple of graphs showing that static limits are much lower than dynamic limits for resistors.

Thanks Paul, that was very fine. It has been very fine being with you for these three years too!!! Thanks again!!!

That's a tough question. Most people have a very large range of different values of 1/4W resistors. Every single one of those different values can handle a different voltage even though they are all quarter watt. Higher value resistors can handle more voltage, but it isn't linear. It takes a lot more resistance of a given wattage rating to be able to handle a little bit more voltage. 1/4W resistors are small, and the capacitors that are about the same size as 1/4W resistors don't have their voltage rating listed on them either. Once you get used to calculating wattage, it's actually pretty easy to calculate if a voltage is too high. Probably easier than trying to find a voltage rating. On top of that, once you know the lowest resistance of a given wattage that you can use for a particular voltage, any higher value resistor is even safer. So you just need to remember/write down the minimum resistance you need for the particular voltage you are working with.

Resistanceseses are futile!

Excellent description, love your videos. Loads of fun being with you also

Good question and good answer. Thanks Paul.

very nice explained !!!thank you

I'm back watching your videos as life got in the way the past week. This is a great and complex question and your demonstration was good but not the whole story. Nice touch including the homemade capacitor and resistor!

@learnelectronics

4 жыл бұрын

You all good my friend?

@michaelpadovani9566

4 жыл бұрын

@@learnelectronics yes thanks for asking, just been crazy busy

A great explanation! thanks.

I recently learned that lots of high value carbon-film resistors are literally incapable of reaching their inferred voltage rating. I was zapping and blowing up stuff with a dangerous DC source, and was unable to get any 1/4 watt resistors above 5.1 MOhm to make it up to 0.25 watts without it immediately going bang. At around 1300 or 1400 volts (if I remember correctly) they became time bombs and would arc over once they warmed up a bit. Above 1400 or 1500 volts, most of them immediately popped. However, I have to say it’s still ridiculously impressive that that size resistors block over a thousand volts without going bang! Especially considering I was testing dirt cheap resistors.

Another good one, thanks!

3years! Well I guess I been her since about the beginning then, congratulations, and HAPPY FRIDAY!

Good stuff!

Well done without going into the more complex regions of capacitance and resistance.

@Erudotic

4 жыл бұрын

Opal Preston Shirley yeah, indeed I was wondering In particular also about inductance when the spiral came up. But, as you so well put it, good to stay away from all those complications when answering such an elementary question

Good Analogy on resistor voltage limits. Sorta Missed Arc Over . Arc Over is issue with Resistors as well.

Many thanks. 👍

Great video, thanks. Explained many things. Do you have any similarly formatted videos on X and y type capacitors and how they fail open or closed? 😁

Love ur vids mate. Keep 'em comin'.

thank you

Very good video

This is plain incorrect. 1/4W resistors usually have only a 300V or 350V rating that is not dependent on Ohm's Law or power at all. For larger voltage rating, bulkier resistors need to be taken, i forget the specifics. SMD resistors have lower voltage rating which also depends on the size. An arc can occur if there's plenty of voltage, it can go through the core material, through the paint on top of the resistors, through the PCB underneath, so for example terminal distance is one of the main factors. It's generally specifically relevant with resistors of very high value, like over 1 Megaohm, as the arc formation voltage rating is easily exceeded before the power rating is exceeded. Slight inductive trait of metal film resistors can also promote arc formation.

@salat

4 жыл бұрын

True (try multiple kV and some tiny xx GigOhm resistors - fun guaranteed) & another reason why you read the datasheet of your parts - you'll find voltage rating for your resistors there..

Thank you....

Where I shop on Mouser and Digikey, resistors have voltage ratings listed in their specifications. And I check before purchasing because I service vacuum tube equipment which has high voltage.

Yes resistors do have a "working voltage" rating. But has been said that a resistor (by itself) is really only limited by heat and not actually the voltage.

Im trying to make a channel entry like yours, i like it it's different 😊.

You're the best,love you., keep it up!

Unique video. Sir can you explain how UJT works practically.

Paul, thank you for all your helpful videos. I wanted to point out a small correction here. I think you noticed that something was wrong when 1^2 mysteriously turned to E^2 between 10:04 and 10:05, but that didn't quite fix the problem. Starting with P=E^2/R, and P=1Watt and R=1000Ohms, you can already calculate the maximum voltage (without need of specifying a current) as E=sqrt(PR)=sqrt(1000)=31.6Volts (as previously pointed out by ats89117). This gives a max current of I=E/R=31.6/1000=.0316=31.6mAmps. As you mention, it would take 100Volts to put 0.1Amps through the IKOhm resistor, which would be asking the resistor to dissipate 10Watts and would probably fry it. It looked like you might have accidentally started to substitute the 1K of R in place of the E variable in the equation, which sent you off on a current tangent. Don't stress about it, we all make mistooks ;) Keep up the great work.

Resistors are often power limited but they have voltage rating too. Something like 0805 or 1206 smd resistor is probably rated for 125V or 200V. Similarly normal 0.66W resistors can be rated for as low as 200V or 300V. When you use higher voltages (say a 350V charged mains capacitor bleader resistor) you may run into limits. A 350V cap needs 2 to 4 0805s in series in order not to break down. In pulsed applications average power can be low too even if voltage spikes are very high. In low voltage stuff like any device less than 100V voltages you are practically power rated. Above that you may run into voltage limiting too. When you get into the kilovolt or more range (that includes some mains snubbers etc), you need to consider voltage rating. When you get into kilovolts range, you are often voltage limited (not power)There are resistors for something like 3kV or 6kV that are easily available. Above that they start to get very expensive. At 10kV and more range, voltage flashover becomes an issua. I think I have one resistor rated for 150kV/1000Gohms and you can guess it is pretty long, even if it is made to be used potted or immersed in oil or some other insulator.

Wow! Now I know what I am going to do with all those squiers and packing peanuts I have ... I'm going to make me some wood resistors for my woodworking projects... Nice... Thanks Paul... Lol Love the video some great stuff... I was waiting for you to unroll that 10v cap... :- ) LLAP

Resistors have a voltage rating & a safe working area defined by the wattage . The voltage rating can be 50 V for ¼ watt resistor . In this low voltage world it's never a headline number . It can be omitted from data sheets but if you know the manufacturer ask the question you will find the answer . With unknown parts you normally find out the hard way . This is why the ht & eht of old TVs used 2 watt carbon resistors .

A question about you analog resistor...packing peanut and scure...in an actual resistor does the wire/scure..go all the way thru?

Assuming no current limiting, a 1k Ohm 1watt resistor has a voltage limit of 31.6v.

when are you going to do a review of the the multimeter that your new sponsor has for sale, Circuit city?

What formula do you use to find the Max Voltage and Max Current in a 1Watt,2watt,5watt,10watt resistor. You can use I X R to find the voltage and V/R to find the current but this is not the max voltage and max current before damaging the resistor at its rated wattage value.

That's a good question...actually resistors do have an absolute maximum voltage regardless of resistance value. See a sample datasheet >> www.digikey.com/en/datasheets/vishay-bc-components/vishay-bc-components-pr010203 notice for the PR01 series the max is 350v for the range 0.22 ohms all the way to 1M ohm. So if I put 500v across one of these 1M babies it's only 0.25W well within the 1W max but exceeding the voltage spec by 150v. So that is an example of exceeding the voltage range but well within the power range. Likewise for low values of R with high currents you can exceed the power limit while staying well within the voltage limit. Moral of the story if you are designing any HV or HI circuits you need to be mindful of both the power and max voltage rating, and possibly any surges or spikes the circuit might encounter. For most small signal, low voltage or digital circuits unless a heavy load is being powered the common 1/4 or 1/2 watt resistors are fine 90% of the time. Remember P=E(sq)/R = I(sq)R image.slidesharecdn.com/internalresistancepowercombiningresistors-120421013549-phpapp01/95/52-internal-resistance-power-combining-resistors-6-728.jpg?cb=1335190002

So a 1/8W 22M resistor is OK for 1,65kV?

I love the way you explain things. Thanks!

@redahugo7286

4 жыл бұрын

me too

If anyone wants an example of a natural capacitor failing by arcing, you just need to look at the sky during a lightning storm, especially if the ground gets hit by lightning: the clouds and the ground act as plates, and the atmosphere is your dielectric.

Good game.. Make sence .. Peace ✌️.

Wait. A 1k resistor with 100v applied to it means the current is 0.1A which means the power (P)=.1A(100v)=10 watts, which exceeds the power rating of a 1W resistor. Did I miscalculate something?

6.5cm x 2.5cm. Good boy, spoken in metric.

@learnelectronics Dear Paul. Been watch videos where people use the 'avalanche effect'. Is there a better circuit than that? My friend used a flip flop circuit with one of the LEDs swapped for a diode. We prefer to do that instead.

They have voltage rating ya just have work a little harder to get it.. you have WATT rating, and color coded rating for Resistance, OMH'S LAW WLL TELL HOW MUCH THE RESISTOR CAN TAKE THERE FOR VOLTAGE RATING/TOLERANCE RATING, YOU PICK... you will know your voltage check your current, multiple. and RATING! SO CHECK AGAINST WATT RATING... HOPE THIS HELP'S I'M VERY DRUNK!!

Doing such calculations on the resistors before connecting prevents a smoked resistor..

Your math isn't too good. V^2 / R = 1 means that V^2 = R so V^2 = 1000 and v = sqrt(1000) which is about 31.6V and NOT 100V. You can check it by multiplying v = sqrt(1000) by I which is equal to V/R which is equal to sqrt(1000) / 1000. This gives a power of sqrt(1000) x sqrt(1000) / 1000 = 1 Watt. Your solution of 100V x 100mA gives 10 Watts, releasing the magic smoke from your 1 Watt resistor... You also missed a great opportunity to gain additional subscribers by not demonstrating the problems with overvolting by blowing up the components!

Resistors are rated in watts because they are current limiters?

@trelligan42

4 жыл бұрын

That is a true statement, though I haven't heard it expressed this way before.

Video starts at 7:05

Can you please explain to me how do you measure the voltage of a charging battery because wouldn't you just be measuring the charging voltage for a battery when you put a multimeter between the power rails when charging a battery? Please get back to me I need to know for a project

@SianaGearz

4 жыл бұрын

Well your question doesn't make sense. The voltage between the battery terminals, as the current is being applied to charge the battery, is specifically the 'voltage of the charging battery'. It may at times be difficult to draw conclusions from, for example, you model your battery as a container with an "ideal" battery in it and a series resistance, also known as ESR. But since you can not get inside the battery, you don't have attachment points to measure the voltage of "ideal" battery inside. Also surprise, the "ideal" battery was a lie all along, and the ESR is dependent on a million things, like the temperature, the current, the charge state, on what the dog had for breakfast, etc, and it changes by several orders of magnitude. So you have a few ways of dealing with it, a few tricks. But first i have to ask you, where does specification of "voltage of the charging battery" to be measured come from, how is it substantiated? What do you want to actually KNOW from that? If it just says that you need the voltage because the spec says so, well just measure the voltage and be done with it, let it be someone else's mistake when it turns out to mean nothing Also what cell type, chemistry battery even.

@trelligan42

4 жыл бұрын

The voltage of a discharged battery is quite low, and no charger will force (say) 1.5 V on a discharged AA battery - a discharged battery would overheat and you need to be wearing goggles. It's true that the charging voltage of a battery is not the whole story. To get a better idea of what's going on, you have to measure the charging current as well. Level 1 chargers (my own name for the simplest chargers) are a voltage source and a resistor in series with the battery. The resistor limits the current to some safe value, and the battery's voltage will rise as it charges. Level 2 chargers provide a variable voltage and use the current to decide what the applied voltage will be. They may also have a 'trickle-charge' capability; when the battery's voltage reaches the full-charge specification, the charger reduces the voltage so the current is very low, as desired for maintaining the voltage. [Most USB chargers do not have trickle charge, so don't leave your phone on charge forever.] Level 3 chargers are more complex, and track the charging cycle over time. These can find problems with the batteries and let you know when they're bad.

V=IR AND P=I*I*R.. These tells you the voltage indirectly ....

Blue moon of Kentucky dots

10:22 Errr, what? 100mA through a 1kOhm resistor is gonna cause that resistor to go up in smoke pretty quickly - I^2*R gives you 10W of power to dissipate, which is gonna fry that poor 1W resistor.

But SMD resistors have voltage rating

1w / 0.1a = 10v 10² v/ 1k ohms = 1w It's 10v not 100v 😉

@ARMYStrongHOOAH17

4 жыл бұрын

Kinda like 6:26 was 50v not 10V. But I can understand a simple slip of the tongue, the math though was confusing the shit outta me. 😂, I thought I was going crazy.

OPENING SOME RESISTORS HAVE NICHROME WIRE IN IT

@learnelectronics

4 жыл бұрын

We didnt cover wire wound resistors. As I mentioned there are thousands of types of resistors.

9:48 why did you say 1k resistor, and 1 watt, and then proceed to substitute the 1 in volts at the top and leave R? Makes no sense...

Why do keep switching terms in your explanation of one law with out explaining it?

@em0_tion

4 жыл бұрын

cause he's human

because they have wattage ratings, duh

You measured that in metric what about us that comes from a country that has put people on the moon😃

@worstuserever

4 жыл бұрын

Those people were put on the moon using only metric units, and the rocket science mostly came from Europe.

@peterdavidson3242

4 жыл бұрын

And if putting people on the moon infers how smart you are then you shouldn't have any issues with simple conversion