OHMS law where do these formulas come from

[swc]

Hi
I currently studying 2330 Lv3 to become an electrician. I've never understood where these formulas come from. I've always managed to get by just taking them for granted. Never really did use them at Lv2. With a 50% failure rate nationwide it's crucial for me to be able to remember these formulas.

R x I (squared)
V(squared) / R
square root(P x R)
p/ I (squared)
V(squared)/p

I understand what's squared and square root means, I don't understand how the formula becomes to be V(squared) /p for example
I'm assuming they're transposed some how from a formula. I would appreciated it if you could shed some light on this. Driving me nuts.

 

[Knobhead]

Google

 

[oxocube]

V-i--r-w
10-2-5-20

 

[Silly Sausage]

1: R x I (squared)
2: V(squared) / R
3: square root(P x R)
4: p/ I (squared)
5: V(squared)/p

They're variations of the power equation P = I x V, replacing I or V from V = I x R
1st one: P = I x (I x R) = I^2 x R

2nd: P = V x (V/R) = V^2 / R

3rd: I^2 = P / R, I = sqt(P / R)

4th: R = P / I^2

5th: R = V^2 / P


Edited after mistake spotted by JUD, see post 25. Thanks mate!

 

[Silly Sausage]

V-i--r-w
10-2-5-20

You've completely lost me with that!

 

[ian.settle1]

You've completely lost me with that!

Well the pubs have opened:77:

 

[ackbarthestar]

You've completely lost me with that!

Its his bank sort code where he would like you to make an advanced payment for more info.

 

[ackbarthestar]

Hi
I currently studying 2330 Lv3 to become an electrician. I've never understood where these formulas come from. I've always managed to get by just taking them for granted. Never really did use them at Lv2. With a 50% failure rate nationwide it's crucial for me to be able to remember these formulas.

R x I (squared)
V(squared) / R
square root(P x R)
p/ I (squared)
V(squared)/p

I understand what's squared and square root means, I don't understand how the formula becomes to be V(squared) /p for example
I'm assuming they're transposed some how from a formula. I would appreciated it if you could shed some light on this. Driving me nuts.

There is two formula here
1/ Ohms Law V=I*R
and
2/ Joules Law P=V*I

By combining them (the power laws) you are now able to solve problems like heat dissipation in resistors P=I^2 *R and cold resistances of heating elements R=v^2 / P.

It'll come to you as you work through some examples.

Might I recommend a couple of electrical books : Electrical Craft Principles Vol1 and Vol2
Probably the best electrical books for level 3 theory on the market.

 

[oxocube]

You've completely lost me with that!

Its easier to remember virw = 10,2,5,20 than it is to remember all the combinations of ohms law. As in 10 x 2 = 20 that means v x i = w etc.

 

[Knobhead]

Where does the 5 come in to it. Still lost me, but we all have our way of remembering things.

Sorry just re-looked at it. Strange way to do things, but, hey ho

 

[Silly Sausage]

Its easier to remember virw = 10,2,5,20 than it is to remember all the combinations of ohms law. As in 10 x 2 = 20 that means v x r = w etc.

Oh, I see, it's one those memory things.
I can never remember them.
Cheers!

 

[pmac10]

2330 L3 has a 50% failure rate? is that really true?

 

[fuzzydunlop]

Wouldn't surprise me 301 is harder than 203 (most failed exam on lvl 2) and the two final exams are 2 1/2 hrs of writing

2330 L3 has a 50% failure rate? is that really true?

 

[pmac10]

not being funny Fuzzy, but when doing an engineering apprenticeship years ago most exams where 2hrs upwards and written and every couple of months. the reason i ask was because i've seen apprentices 'forced through', ie keep handing it in until its right.
have you seen any thing like that? sorry op for getting of subject, just remain calm and this hijacking will be over before you know it:rifle:

 

[SPARTYKUS]

And the 2391 has a what failure rate..... Oh! sorry its being done away with.