Hi guys! If you are looking for extra practice questions, I made a huge problem set of my own problems with detailed solutions. Check it at my online shop here: koji.to/k/9uCs
Well done! It is so, so annoying that different exam boards can't agree whether the absolute uncertainty is the smallest graduation, or half the smallest graduation. AQA and Edexcel for example.
@@leuanjennings9929 Yep! AQA uses half of the smallest measurement value (that's what I used at university too when I was in a lab and it's pretty sensible! )
I am so certain about uncertainties now . Thank you so much for this explanation .. those are the parts of this concept that I always cofuse and forget ❤ ( equations containing uncertainties)
5:00 Even if you are subtracting the total do you subtract the total when working out the percentage uncertainty? So if you wanted to find the extension would the equation for the percentage uncertainty be (Absolute uncertainty /extension) or (absolute uncertainty/ original length + new length)? Thank you
I'm confused, what reason is there to add or take away, multiply or divide or raise to a power? How do I know which one to do? I don't think I'm getting the "why's". Why are we doing this?
Excellent question! So...absolute uncertainties - we can just add them as we have they have the same units. E.g. mass +mass can gives us kg+kg which is also kg. If we have speed , v=d/t we can't just add meters+seconds in physics. So we convert them to percentages which are dimensionless (unitless). If we raise something to a power, we are essentially using it twice or three times or whatever the power is. e.g. I^2 = I*I so we use it twice, so we multiply the uncertainty by 2. Hope this helps!
Thank you for the explanation! Say you measured a length of wire with diameter: 0.27mm (+-) 0.01mm. And you wanted to divide by 2 to get a value for the radius, what would you do to the uncertainty?
If you are after the radius just divide the value by two but you retain the same uncertainty. So the radius would be 0.135 +- 0.01 mm as you only consider the value you measured.
Hi sir, i have my physics practical in a few days and i see a lot of questions on estimating the percentage uncertainty. Could you please explain to me how I'd approach this question 🙏
For the beginning example of 5.46 V +/- 0.001V, I know we can’t fully trust the last digit, but it wouldn’t between 5.45 and 4.47. If the actual value was 4.453, the reading would show as 4.45V, not 4.46V, so shouldn’t it be between 4.455 and 4.465, as anything in that range would round to what you would see on he voltmeter, meaning the uncertainty is +/- 0.005? The uncertainty is only the same as the resolution of the instrument you are using requires two measurements to get a value, like a mm ruler. You would measure something from 0mm to another value mm, but where you put the ruler on 0 still has an uncertainty of +/- 0.5mm, so you are adding the uncertainties of the value you have measured and the 0mm uncertainty to get an uncertainty equal to the resolution. With things like mass balances that are digital, we assume that it is always zeroed correctly so there is no need to account for 0 value uncertainty
@zhelyo_physics no what I meant is, that this 0.1 has + and - right, then why are we doing calculations using the + 0.1 and not the -0.1? Thanks and have a nice day
With your ruler analogy at the start, you state the resolution to be 1mm. Would the absolute uncertainty not then be 0.5mm. You state as much in your note but verbally you said it was still 1mm
interstingly that depends on your exam board. At university I always took the resolution to be half of the smallest measurement, AQA typically does that, OCR in A Level Physics takes to be 1 of the smallest measurement. Hope this helps!
The edexcel spec lists it for a ruler as half the smallest measurement (half the resolution). It also lists the definition of resolution as the smallest reading possible. You can also calculate it as half the range of the data if you are given a lot of measurements and no uncertainty. Hope this helps!
How would you find the percentage uncertainties of an average. For example you're given 5 measurements for the thickness of something and are asked to find the percentage uncertainty given that the measurements are to 3 significant figures
I have actually filmed the answer to this: ua-cam.com/video/WOckc29sZJA/v-deo.html this link should take you to the correct timing, but have a look at the time stamp, uncertainty of a data set.
All the theory is covered, I would do lots of practice problems next! I have some here: ua-cam.com/video/vhdI0eZf5nY/v-deo.html Thanks a lot for the comment! : )
hey I've got this question on my homework that I need help with. it says the uncertainty is 2mm but doesn't say + or - so I'm unsure whether it means +or-1mm or +or-2mm
@@zhelyo_physics but i thought that wasnt the uncertainty i thought that was the value u measure do you still always add it even if the question is substract
Do you mean absolute or percentage uncertainty? As I mentioned we always add uncertainties in both cases. If we add or subtract things we add absolute unc. If we multiply or divide we add percentage unc.
@@erfrerferfrere if we take away the voltage it would be 5-4 = 1V but this is the voltage, not the uncertainty. The uncertainty would still be the same, 1V +- 0.3 V
The edexcel spec lists it for a ruler as half the smallest measurement (half the resolution). It also lists the definition of resolution as the smallest reading possible. You can also calculate it as half the range of the data if you are given a lot of measurements and no uncertainty. Hope this helps!
depends on the problem, think of the fractional uncertainty as a percentage uncertainty and follow the rules in the video depending on the situation : )
@@vaster1142 yep! If you raise it to a power this is equivalent to multiplication, i.e. you have to ad the percentage uncertainty similarly to other rules. Hope this is helpful!
the rules for uncertainties are extremely similar across all a levels : ) yes it is applicable however you should use your specification/syllabus as a checklist when going through this. Hope this helps!
@@zhelyo_physics well my syllabus says students are not expected to compound percentage uncertainties. Is compounding uncertainties same as combining them?
Mostly. Around 95% So I design them so that they can be applicable with every exam board. I recommend downloading the specification and ticking concepts as you revise them. Good luck, drop a comment if something doesn't make sense!
it's microsoft whiteboard which is free, since filming the video though the software has become a lot slower, there might be better alternatives, but it's still quite good!
I actually have a huge amount out already but will constantly be expanding them - here is a step by step guide for paper 3: ua-cam.com/video/kewwyTfUc_U/v-deo.htmlsi=ti6V1AVPl35n6M-m Have a browse through the channel, I also have lots of questions from paper 3 and all the content filmed.
Hi guys! If you are looking for extra practice questions, I made a huge problem set of my own problems with detailed solutions. Check it at my online shop here: koji.to/k/9uCs
This was explained very succinctly and coherently - thanks.
Anytime! Glad to hear this!
Who takes physics and english a levels at the same time bro....
🤓🤓🤓
@@fatimamohamed4437 🤣
I'm grateful beyond measure for this explanation, it helped me a lot
glad to hear this! : ) thanks for the comment!
Excellent video, cleared up all the confusion I've had around uncertainties. 👍
thank you so much for the comment! Glad to hear!
best of the best explanations i can't find a way to thank you !!!!!
Glad to hear! Thanks a lot for the comment!
Indeed this was a great video I couldn't understand the topic for the whole of last year thanks
thanks a lot for the kind comment!
Amazing Video. Clear and Precise. Love it!!!!
thank you so much!
this was a very good video sir easily and concisely explained helped much more than any other video ive seen Cheers!
the dreny parrots
Thanks a lot! Much appreciated!
Well done! It is so, so annoying that different exam boards can't agree whether the absolute uncertainty is the smallest graduation, or half the smallest graduation. AQA and Edexcel for example.
Totally agreed! Thanks for the comment!
Do you know what aqa want?
@@leuanjennings9929 Yep! AQA uses half of the smallest measurement value (that's what I used at university too when I was in a lab and it's pretty sensible! )
Would anyone be kind enough to tell me what OCRA wants or tell me where to find out? thanks
OCR takes absolute uncertainty to be +- 1 of the smallest measurement
This video was very informative and helped me understand uncertainties I don't know what I would do without you
fantastic to hear! Thank you for the comment!
Thank you so much you are an absolute legend! My teacher cannot teach this at all
I am so certain about uncertainties now . Thank you so much for this explanation .. those are the parts of this concept that I always cofuse and forget ❤ ( equations containing uncertainties)
Thank you so much for the comment! Glad this is useful!
Thank you so much. You've saved my classmates and I from possibly failing a quiz 😭
Anytime! Glad to hear this is useful!
I am so grateful for this video, it helped me a lot in clearing out my concepts. Thank you so much!
Anytime! Thank you for the kind comment!
thank you so much, now I certainly feel more confident on uncertainties.
great to hear! thanks for the comment!
Missed chance to say now I'm certain about uncertainties
This video explains much more better than my teacher, thx!
anytime! thank you for the comment
5:00 Even if you are subtracting the total do you subtract the total when working out the percentage uncertainty?
So if you wanted to find the extension would the equation for the percentage uncertainty be
(Absolute uncertainty /extension) or (absolute uncertainty/ original length + new length)? Thank you
Great question! It would be ( abs uncertainty in new length/new length + abs uncertainty in original length/original length )x 100
this was so genuinely clear and helpful
Thanks a lot for your comment! Much appreciated!
Im certainly certain of the uncertainties after watching your videos! 😄
Certainly great to hear 😆
very helpful sir. thank you very much!! you are a life saver
anytime, thanks for the comment!
Watched so many videos this was the best
thank you so much!
I'm confused, what reason is there to add or take away, multiply or divide or raise to a power? How do I know which one to do? I don't think I'm getting the "why's". Why are we doing this?
Excellent question! So...absolute uncertainties - we can just add them as we have they have the same units. E.g. mass +mass can gives us kg+kg which is also kg.
If we have speed , v=d/t we can't just add meters+seconds in physics. So we convert them to percentages which are dimensionless (unitless).
If we raise something to a power, we are essentially using it twice or three times or whatever the power is. e.g. I^2 = I*I so we use it twice, so we multiply the uncertainty by 2. Hope this helps!
@@zhelyo_physics Ohh thank you so much! This helps alot
Best explanation ever!
thank you very much!
This was super helpful, thank you!
anytime, thanks for the comment!
Thank you for the explanation! Say you measured a length of wire with diameter: 0.27mm (+-) 0.01mm. And you wanted to divide by 2 to get a value for the radius, what would you do to the uncertainty?
If you are after the radius just divide the value by two but you retain the same uncertainty. So the radius would be 0.135 +- 0.01 mm as you only consider the value you measured.
Thanks a lot for this informative video. The content was understandable and made me clear about the uncertainties ideas ☺️
Anytime, glad this was useful
0:30 which exam boards use half, and which don’t? do you know for edexcel?
Edexcel practical handbook would give the resolution as the smallest reading you can take, the uncertainty being half of the value.
@ okay, thanks!
Greatness from this guy👑
haha thanks, glad this is helpful!
plenty of thanks, you did deserve it
thank you for the kind comment!
Many thanks for making the vedios. It is really usful for my coming physics unit quiz!
anytime, glad this is useful!!
Hi sir, i have my physics practical in a few days and i see a lot of questions on estimating the percentage uncertainty. Could you please explain to me how I'd approach this question 🙏
Thank you so much for this explanation!
anytime! thanks for the comment!
Thank you so much! Super clear and easy! ❤
Anytime! Thanks for the comment!
at 5:30 isn't the total voltage 5+5+4
For the beginning example of 5.46 V +/- 0.001V, I know we can’t fully trust the last digit, but it wouldn’t between 5.45 and 4.47. If the actual value was 4.453, the reading would show as 4.45V, not 4.46V, so shouldn’t it be between 4.455 and 4.465, as anything in that range would round to what you would see on he voltmeter, meaning the uncertainty is +/- 0.005?
The uncertainty is only the same as the resolution of the instrument you are using requires two measurements to get a value, like a mm ruler. You would measure something from 0mm to another value mm, but where you put the ruler on 0 still has an uncertainty of +/- 0.5mm, so you are adding the uncertainties of the value you have measured and the 0mm uncertainty to get an uncertainty equal to the resolution. With things like mass balances that are digital, we assume that it is always zeroed correctly so there is no need to account for 0 value uncertainty
Thank you for adding subtitle❤
when we were making calculations using the uncertainity, why were getting the value for the + only and not the -?
you can think of it as the absolute value, i.e. if the absolute uncertainty is 0.1, then 5+-0.1 gives the range between 4.9 and 5.1 Hope this helps !
@zhelyo_physics no what I meant is, that this 0.1 has + and - right, then why are we doing calculations using the + 0.1 and not the -0.1? Thanks and have a nice day
thank you so much! im understanding this one day before my exams haha
Anytime!! Good luck for your exams!
what about going from a diameter to a radius sir? Do you assume that the %uncertainty is the same rather than the absolute (ie absolute halves)?
excellent point. Nope the percentage uncertainty in the diameter is twice as small as the measured value is twice as big.
With your ruler analogy at the start, you state the resolution to be 1mm. Would the absolute uncertainty not then be 0.5mm. You state as much in your note but verbally you said it was still 1mm
interstingly that depends on your exam board. At university I always took the resolution to be half of the smallest measurement, AQA typically does that, OCR in A Level Physics takes to be 1 of the smallest measurement. Hope this helps!
thank you , pls keeping on making useful videos
Thanks a lot for the comment, much appreciated!
at 3:36 why were you able to just half it to get the absolute uncertainty?
(rather than using p.u equation)
actually just a coincidence, I just took 5% of 50 which happens to be 2.5. Excellent question!
@@zhelyo_physics ohhhhhhhh, makes so much sense then haha
Great video , thanks ❤
Anytime! Thanks for the comment!
Thank you 😭😭🙏🏻❤️
anytime, thank you for the comment!
do we need to know the level of confindence? and how to calc it for AS physics?
Depends on the syllabus/exam board, I always recommend using it as a checklist.
0:29 What does Edexcel assume it is?
The edexcel spec lists it for a ruler as half the smallest measurement (half the resolution). It also lists the definition of resolution as the smallest reading possible. You can also calculate it as half the range of the data if you are given a lot of measurements and no uncertainty. Hope this helps!
@@zhelyo_physics Ah, I see, thank you.
Thank you!
anytime!
Really well explained😁
thanks a lot ! Much appreciated!
Thank you I love you 🙏🏾🙏🏾
haha anytime!
How would you find the percentage uncertainties of an average. For example you're given 5 measurements for the thickness of something and are asked to find the percentage uncertainty given that the measurements are to 3 significant figures
I have actually filmed the answer to this: ua-cam.com/video/WOckc29sZJA/v-deo.html this link should take you to the correct timing, but have a look at the time stamp, uncertainty of a data set.
@@zhelyo_physics This helped me gain a mark today, thanks.
Do we take half the smallest reading or the smallest reading for Uncertainty in OCR A?
OCR A usually the smallest reading is the absolute uncertainty unless stated otherwise in the question
Thank you so much
anytime!
I and no longer uncertain
wohooo : ) Great to hear : )
Thank you so much sir
Is this video enough if I fully understand it for a level physics uncertainties?
All the theory is covered, I would do lots of practice problems next!
I have some here: ua-cam.com/video/vhdI0eZf5nY/v-deo.html Thanks a lot for the comment! : )
hey I've got this question on my homework that I need help with. it says the uncertainty is 2mm but doesn't say + or - so I'm unsure whether it means +or-1mm or +or-2mm
Uncertainty is always +- , a measurement of 5 mm +- 2mm means the real value is somewhere between 3 mm and 7 mm . Hope this helps!
u see the adding or subtracting resistance example if it was subtracting would it be 5-4=1 or still adding the a uncertainties to get 5+4=9
excellent question, we always add uncertainties.
@@zhelyo_physics but i thought that wasnt the uncertainty i thought that was the value u measure do you still always add it even if the question is substract
Do you mean absolute or percentage uncertainty? As I mentioned we always add uncertainties in both cases. If we add or subtract things we add absolute unc. If we multiply or divide we add percentage unc.
@@zhelyo_physics apologies for the confusion check 5:30 of the video if the question was subtraction would it be 5-4 or still 5+4 to get 9
@@erfrerferfrere if we take away the voltage it would be 5-4 = 1V but this is the voltage, not the uncertainty. The uncertainty would still be the same, 1V +- 0.3 V
Do we take smallest value or half the smallest value in uncertainties foe edexcel IAS
The edexcel spec lists it for a ruler as half the smallest measurement (half the resolution). It also lists the definition of resolution as the smallest reading possible. You can also calculate it as half the range of the data if you are given a lot of measurements and no uncertainty. Hope this helps!
Thank you sir 🙏🙏
anytime!
Gud job... 🤝🤝
thanks!
Thank u so much:33
anytime! thank you for the comment!
What if u are given two values and both have uncertainty.,how can u find the fraction uncertainty.... 🙏🙏
depends on the problem, think of the fractional uncertainty as a percentage uncertainty and follow the rules in the video depending on the situation : )
Can we also do these using the formula
Max-original
Which formula exactly?
Are you sure it's in and not Ln? Cos using differential calculus ( since most uncertainties are very close to 0), it's Ln
for which part of the video exactly sorry? We don't tend to bring in calculus as we normally know the uncertainty exactly from our instrument.
@@zhelyo_physics 8:22
@@vaster1142 yep! If you raise it to a power this is equivalent to multiplication, i.e. you have to ad the percentage uncertainty similarly to other rules. Hope this is helpful!
Is this for edexcel ial unit 3 too?
the rules for uncertainties are extremely similar across all a levels : ) yes it is applicable however you should use your specification/syllabus as a checklist when going through this. Hope this helps!
@@zhelyo_physics well my syllabus says students are not expected to compound percentage uncertainties. Is compounding uncertainties same as combining them?
do u have videos for your solved Past papers or topical papers for AS Level Physics (9702) syllabus Cambridge?
Hi sadly no past papers walkthroughs.
@@zhelyo_physicsdoes your playlist contains all the videos for AS Level (9702) updated syllabus for Cambridge
Mostly. Around 95% So I design them so that they can be applicable with every exam board. I recommend downloading the specification and ticking concepts as you revise them. Good luck, drop a comment if something doesn't make sense!
pls sir how did you get 11% in the multiplication and division practice example. i used my calculator but it didn't work
Did you use 1.1? I redid it and it's okay. 0.1/5.0*100+0.1/1.1*100 Hope this helps!
for the resistance question, would the final answer of it be 4.5 +- 11%??
correct! well done!
@@zhelyo_physics ok great, this doesnt seem too bad. thank you so much for your vidoes
Amazing
thank you for the comment!
am i correct in saying for the last question that the absolute uncertainty of the volume is +- 4.8m^3? Great video by the way!
You are certainly correct!! : )
What software r u using its actually good
it's microsoft whiteboard which is free, since filming the video though the software has become a lot slower, there might be better alternatives, but it's still quite good!
@@zhelyo_physics Thank you, sir.
much clear than my teacher
Thank you for the comment!
Hey, can you consider making videos for paper 3
I actually have a huge amount out already but will constantly be expanding them - here is a step by step guide for paper 3: ua-cam.com/video/kewwyTfUc_U/v-deo.htmlsi=ti6V1AVPl35n6M-m Have a browse through the channel, I also have lots of questions from paper 3 and all the content filmed.
Thank youu
You have earned yourself a subscriber
@@zhelyo_physics
Nice lecture 🌝
Thank you for the comment!
thanks :)
No problem!
exam in an hour and 30 minutes 😅
tysm
anytime!
What if there is negative power
excellent question - for this I would calculate half the range, using this method: ua-cam.com/video/swsLwIyrzQo/v-deo.html
🎉
good, but video could be shorter.
ua-cam.com/video/6FgjfvW1LH8/v-deo.htmlsi=997NOKOXl-fR8LsD here are the rules in 1 minute : )
Get a better mic plz
I did! : ) Thanks for the suggestion.
@@zhelyo_physics yes I see, think you could re-record the audio for this?