Transposing formulas

[training_spark]

Hi

whats an easy way of working out where everything goes when you transpose a formula ?

e.g

if you had to work out the number of primary turns how do you know where to re arrange everything

is = up = np

- - -

ip us ns

thanks

 

[Sidewinder]

One thing for simple formulae, change the side change the sign.

If the "thing" crosses the = sign it changes its sign.

add (+) becomes subtract (-), multiply (x) becomes divide (/)

Any use?

 

[Apache]

Have you seen Admin's formula sheet - use triangles for the three way formulae

http://www.electricianforum.co.uk/electricalformulas.html

eg

Just cover the number you want to find!

When dealing with more complex formulae my approach varies on the example.

eg

you would be given primary voltage (say Up= 240V) and secondary voltage (say Us= 12V). If we knew any other piece of information, eg 100 turns on primary coil.

so we know that the ratios are proportional, so Up/Us = 240/12 = 20

Now we know that Np/Ns = 20 AND Np = 100, so Ns = 100/20 so Ns = 5

Does that make sense??

 

[training_spark]

thanks for the advice, some of it makes sense now, what still confuses me is how do you know what order to place things if e.g working out secondary turns :

ns= ___________

how do you know what ones to use on the top for multiplying and what one it is devided by on the bottom?

thanks again

 

[Sidewinder]

depends which other values you have, difficult to put equations up on here but:

Ns= ((Np Us) / Up) = ((Np Ip) / Is)

HTH and makes sense!

 

[Apache]

thanks for the advice, some of it makes sense now, what still confuses me is how do you know what order to place things if e.g working out secondary turns :ns= ___________

how do you know what ones to use on the top for multiplying and what one it is devided by on the bottom?

thanks again

You just have to learn the formula!

 

[training_spark]

You just have to learn the formula!

i know haha