When I was at college I always remember trainee sparky's struggling with those tables in the regs book, I found them easy to be honest, but it depends how your mind works with maths and graphs I suppose. Another great video JW thanks :-)
Nicely presented and good clarity, great refresher for my neck top. Another plus for Logs, and log graphs is showing better detail at lower orders, my apologies if this was conveyed eloquently by Mr Ward.
John......you definitely missed your vocation. Lots of people (including me) struggle with logarithms and log graphs, but you explain it really well here. Thanks
Sorry for a silly, unrelated question. I always thought a 5 A fuse would melt if the current is over rms5A for a few seconds. Your graph for the 5A fuse shows that even rms 9 A could be applied to the fuse indefinitely without the fuse blowing.... What does that 5A rating mean? Is the same found with circuit breakers, do they permit far more current than indicated by the breaker rating?
The rating of a fuse is typically where it can operate indefinitely, with a bit of margin so as to not balance on the edge of blowing (sndd that margin can be surprisingly big) For instance if you turn on a device the initial current may be significantly larger than the operating current due to, for instance, buffering capacitors being charged up from empty. There are also fuses with different behaviour, for instance "fast" and "slow". Fast would be nearer your expected behaviour but not so suitable to situations with inrush currents, where a slow type fuse is better. Also, the construction of most common fuses/breakers just don't lend itself to high precision/close proximity between indefinate operation and blowing. For the details of when they're expected to blow you need the graphs/data sheets. If you need something very precise I'd sooner look at some electronic protection circuit rather than a mechanical fuse.
Very good... I do disagree with one thing you said though. 2:24 a log scale doesn't start at zero... it continues the 10x pattern forever, so the lowest horizontal line shown would be $1.00 and should the need ever arise the log graph could be extended downwards and would show the same great detail if the price of bitcoin entered the $0.10 to $1.00 range or even the $0.01 to $0.10 range... and so on (even if people had lost interest in looking at graphs of bitcoin by then)
In those Bitcoin charts the log tells nicely how your investment changes in value. When the value was small you would buy more. The huge jump at the end of 2013 was almost unnoticeable in linear graph. 7:05 actually the half way between 1 and 2 is not 1,5 but 1,41. Halfway between 1 and any number is the square root of the number. For example 10 is halfway between 1 and 100.
@@wheelwells148 No, if you look at the mid point between 1 and 100, you will find 10, not 50.5. similarly in the mid point of 1 and 2 there is sqrt(2)=1.41, not 1.5.
Another way of looking at is that the same distance on the log scale represents the same percentage difference. In the case of the crypto coin graphs you still have the same % margin if the value changes from $10 to $20 or from $4.000 to $8.000 Also, graphs with one axis linear and one logarithmic are often called Lin/log graphs, to differentiate with log/log graphs where both axis are logarithmic.
John I’m hoping you can explain something - NICEIC question this week was will an 80 short circuit trip a 20 amp breaker - in the regs it says no, it’s 100amps - I thought yes because type b is 3/5 times it’s rating which would give a 20 amp 60-100 amps. Where am I misunderstanding? Thanks in advance
Type B is between 3x and 5x, so 80A for a 20A device is in the 'might trip' category. However for actual installations it's necessary to ensure that it will definitely trip, so a fault current of 80A would not be considered suitable for a typical Type B 20A circuit breaker. 100A would be the absolute minimum, and it would preferably be more than that as things like the supply voltage and ambient temperature will also affect the fault current.
Well done for sharing this John. For most of us engineers/ electricians you'd hope people would already know all this. However this video explains how to read the graphs very clearly, i would like to think this video is going to be used in schools ect... Great video John. Am i able to send an electrical item in to you by any chance? Kyle :)
Shouldn't the half value between 1 and 2 be the same proportion of the way across as 5 is in the 1 to 10 section? It's surely logarithmic at all scales!
Sad state of affairs with 'modern' education if you need to explain the difference between Lin & log. Would love to see the face of kids if you took away their calculators and phones and gave them a log table book and some sums!
Hi could you please make a video regarding bs7671 because I found it a bit difficult to find the answers from it. I am studying electricity at the moment and I will have my bs7671 18 addition exam soon. Thank you.
When I was at college I always remember trainee sparky's struggling with those tables in the regs book, I found them easy to be honest, but it depends how your mind works with maths and graphs I suppose. Another great video JW thanks :-)
Nicely presented and good clarity, great refresher for my neck top. Another plus for Logs, and log graphs is showing better detail at lower orders, my apologies if this was conveyed eloquently by Mr Ward.
Nice explanation for us uneducated in log. Thanks and I still waiting for another elevator review. Happy new year from Tangobaldy.
John......you definitely missed your vocation. Lots of people (including me) struggle with logarithms and log graphs, but you explain it really well here. Thanks
Excellent explanation of why magnitude matters. Good stuff JW!
Sorry for a silly, unrelated question. I always thought a 5 A fuse would melt if the current is over rms5A for a few seconds. Your graph for the 5A fuse shows that even rms 9 A could be applied to the fuse indefinitely without the fuse blowing.... What does that 5A rating mean? Is the same found with circuit breakers, do they permit far more current than indicated by the breaker rating?
spelunkerd.....watch this video by John Ward ruclips.net/video/u6I7dKDk7hE/видео.html in it he explains what a fuse of rating x Amps actually means
The rating of a fuse is typically where it can operate indefinitely, with a bit of margin so as to not balance on the edge of blowing (sndd that margin can be surprisingly big) For instance if you turn on a device the initial current may be significantly larger than the operating current due to, for instance, buffering capacitors being charged up from empty.
There are also fuses with different behaviour, for instance "fast" and "slow".
Fast would be nearer your expected behaviour but not so suitable to situations with inrush currents, where a slow type fuse is better.
Also, the construction of most common fuses/breakers just don't lend itself to high precision/close proximity between indefinate operation and blowing.
For the details of when they're expected to blow you need the graphs/data sheets.
If you need something very precise I'd sooner look at some electronic protection circuit rather than a mechanical fuse.
@@michaeltempsch5282 Good insight into fuse operation.
Very good... I do disagree with one thing you said though. 2:24 a log scale doesn't start at zero... it continues the 10x pattern forever, so the lowest horizontal line shown would be $1.00 and should the need ever arise the log graph could be extended downwards and would show the same great detail if the price of bitcoin entered the $0.10 to $1.00 range or even the $0.01 to $0.10 range... and so on (even if people had lost interest in looking at graphs of bitcoin by then)
In those Bitcoin charts the log tells nicely how your investment changes in value. When the value was small you would buy more. The huge jump at the end of 2013 was almost unnoticeable in linear graph. 7:05 actually the half way between 1 and 2 is not 1,5 but 1,41. Halfway between 1 and any number is the square root of the number. For example 10 is halfway between 1 and 100.
Ummm, you have mixed up Log & Lin.
@@wheelwells148 No, if you look at the mid point between 1 and 100, you will find 10, not 50.5. similarly in the mid point of 1 and 2 there is sqrt(2)=1.41, not 1.5.
Please read your first comment to JW's video..
@@wheelwells148 Compare 0:53 to 2:30. In the first the jump at the end of 2013 is very small. In the second it is very high.
Another way of looking at is that the same distance on the log scale represents the same percentage difference. In the case of the crypto coin graphs you still have the same % margin if the value changes from $10 to $20 or from $4.000 to $8.000
Also, graphs with one axis linear and one logarithmic are often called Lin/log graphs, to differentiate with log/log graphs where both axis are logarithmic.
Nice explanation thanks. When are you going to play that organ?
Miles Bancroft lmao
Perfectly explained 👌
Nicey explained in simple terms.
Thanks John
Thanks John.
Perfectly clear now Thankyou
this is where your screwdriver would have come in handy John haha. Thanks
John I’m hoping you can explain something - NICEIC question this week was will an 80 short circuit trip a 20 amp breaker - in the regs it says no, it’s 100amps - I thought yes because type b is 3/5 times it’s rating which would give a 20 amp 60-100 amps. Where am I misunderstanding? Thanks in advance
Type B is between 3x and 5x, so 80A for a 20A device is in the 'might trip' category.
However for actual installations it's necessary to ensure that it will definitely trip, so a fault current of 80A would not be considered suitable for a typical Type B 20A circuit breaker. 100A would be the absolute minimum, and it would preferably be more than that as things like the supply voltage and ambient temperature will also affect the fault current.
Well done for sharing this John. For most of us engineers/ electricians you'd hope people would already know all this. However this video explains how to read the graphs very clearly, i would like to think this video is going to be used in schools ect... Great video John. Am i able to send an electrical item in to you by any chance?
Kyle :)
Yes, contact details here: www.flameport.com/youtube_channel_info.cs4
2:35 Watching this in 2024 chuckling to myself 😅
Hi John, Could you shed any light on where the disconnection time/value of 0.4s/ 5s for TN systems and 0.2s / 1s for TT came from in the 1st place?
Shouldn't the half value between 1 and 2 be the same proportion of the way across as 5 is in the 1 to 10 section? It's surely logarithmic at all scales!
Please note the fixed globe, made in Italy for some reason, in the background.
Yoo must be on the organic food, very easy to understand for the diyer !!
Was going to try to make a joke with a picture, but it is far more difficult than I expected to find one of a graph made of logs, or even sticks...
Feckin hated looking at log graphs - used to take ages to cop on to what was being represented.
Wow mantap 👍👍👍
Sad state of affairs with 'modern' education if you need to explain the difference between Lin & log. Would love to see the face of kids if you took away their calculators and phones and gave them a log table book and some sums!
Hi could you please make a video regarding bs7671 because I found it a bit difficult to find the answers from it. I am studying electricity at the moment and I will have my bs7671 18 addition exam soon. Thank you.