Why?
It's obvious that the last two can't both be right - otherwise I² would equal V².
Incidentally, why does it space the text correctly in the quote but not in the post?
Ah, it only did that in the reply box; not the post.
Limiting Power Draw from Underfloor heating system
- Thread starter renegadeandy
- Start date
It's obvious that the last two can't both be right - otherwise I² would equal V².
Incidentally, why does it space the text correctly in the quote but not in the post?
Ah, it only did that in the reply box; not the post.
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Hence my second version with triangles.
Tonight I looked through the selection of photos of the white board on his Ipad again, probably 40-50, initially her values, then got each student to nominate 2 values from I, R, V & W. Then she (actually a very young and attractive she) guided them through working out the other 2 values.
Apparently; 25A and 100W = 4V using 2nd & 6.25Ω (should be 0.16Ω) using 3rd but 4V and 6Ω = 0.67A using 1st & 2.67W using 4th.
also; 1A and 15Ω = 15V using 1st & 0.067W (should be 15W) using 3rd but later 15V and 15Ω = 1A & 15W using 4th and allegedly none spotted the similarity or error
I worked through those 2 with him
There were other examples, IIRC 100V/10Ω vs 10A/1KW,
however there were several examples with 1Ω which actually makes no difference to the result if equation 3 is wrong.
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To do it with text, use a [code] ... [/code] tag pair. It makes the text a mono space font and doesn't collapse multiple spaces
Code:
V
I x Retc
Experimenting
Thanks Robin but I'm going to need more info
Well it looks like I've got there but it seems one has to remember a fair bit while typing.
As to whether I remember how for next time is... now was I going up or down stairs
Thanks Robin but I'm going to need more info
Code:
V
IxR W
VxI
Code:
V W I² V²
IxR VxI WxR WxR
[CODE] V W A A
I x R V x I I X I I x I[/CODE]
Well it looks like I've got there but it seems one has to remember a fair bit while typing.
As to whether I remember how for next time is... now was I going up or down stairs
Last edited:
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Why have these confusing triangles ?
Keep it simple Amps = Volts divided by Ohms
Keep it simple Amps = Volts divided by Ohms
Because it's how these formulas are taught in school, at least it was for me.
Take SOHCAHTOA for example...
So that you can see all three equations at a glance.
I = V / R
V = I x R
R = V / I
or create spacing using multiple characters with their text colour change to white
start#######end
start#######end
start#######end
While teaching this particular series ,
thisView attachment 299980
is far easier than this random dozen
R = V² / W
R=W / I²
I = V / R
V = I x R
R = V / I
V = W / I
V =√( W x R)
I = √( W / R)
W = I² x R
W = V x I
I = W / V
W = V² / R
Even if the triangle contents are wrong.
The real question is: Why are my spaces ignored ?
The very first time I learnt the triangle method was:
Promptly followed by:
Then I sat doing homework with a friend and we did this:
to save a step in our calculations and showed that symbol in the working to demonstrate the step taken.
Promptly followed by:
Then I sat doing homework with a friend and we did this:
Last edited:
Multiple spaces are considered by the software to be a waste of space in the forum's data storage area and are thus reduced to only one being stored
At my school we learnt the equations but to enforce them we did experiments with meters, resistance boxes and variable output power supplies.
That's presumably the idea, and it's quite a common 'tool' that is used.
However, I've often wondered whether it is actually doing people an (educational) service by providing them with such 'tools'. Given an equation as simple as:
X = Y x Z
...it requires only an understanding of the most trivial and basic concepts of algebra to be able to re-arrange it in the other two possible ways (to put Y or Z on the left-hand side) - and the great advantage of learning 'how to do it oneself' is that one can then apply that knowledge to much more complicated equations.
The 'triangles' are a sort of 'cook-book' approach - an approach which (at least in my opinion) rarely has a lot to be said for it.
Kind Regards, John
Yes, probably. One of consequent pains in this forum is that, since it doesn't have an 'indent' facility, most attempts to indent anything get frustrated by the forum software!
Kind Regards, John
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