# I blew up the parallel resistor formula!

I tried to use the parallel resistor formula -

1/Rt = 1/R1 + 1/R2 + 1/R3

to calculate a total of three resistors in parallel. One of them was a 270 ohm, and the other two resistors are shown in the attachment and the formula blew up!

au contraire 1/r = infinity so R = 0 notaprob

Bzzzzzzzzzzzzzzttttt....

1/0 is not infinity, it's undefined.

modeller: I tried to use the parallel resistor formula -

1/Rt = 1/R1 + 1/R2 + 1/R3

to calculate a total of three resistors in parallel. One of them was a 270 ohm, and the other two resistors are shown in the attachment and the formula blew up! :fearful:

As the teacher once told you in school, you must show your work! Blowing up is like saying your dog eat your homework. ;)

Lefty

JimboZA: Bzzzzzzzzzzzzzzttttt....

1/0 is not infinity, it's undefined.

As the bottom number gets smaller the reciprocal gets bigger, as this number approaches zero the reciprocal approaches infinity. Only the purest of pure mathematicians would agree with you, engineers would say say it was infinity.

and the formula blew up!

No it didn't. Have you come across the term GIGO?

retrolefty: As the teacher once told you in school, you must show your work! Blowing up is like saying your dog eat your homework. ;)

You want a picture of my HP calculator display?

If I attempt the first 1/R1 it says Divide by Zero error. :(

Only the purest of pure mathematicians would agree with you, engineers would say say it was infinity.

Well I am an engineerâ€¦

Itâ€™s trivial to show that for a/b = c and therefore a =bc, if b = 0 there is no value of c which will satisfy the equation a =bc for the case or a <> 0â€¦, not even infinity; all values of c will satisfy the case of a= 0â€¦ therefore undefined.

Slightly editedâ€¦

modeller:

retrolefty:
As the teacher once told you in school, you must show your work! Blowing up is like saying your dog eat your homework.

You want a picture of my HP calculator display?

If I attempt the first 1/R1 it says Divide by Zero error.

That was simply a user input error, as there are no zero ohm resistor, certainly not a room temperature. Put in the real resistance values and it will work.

Lefty

retrolefty: That was simply a user input error, as there are no zero ohm resistor, certainly not a room temperature. Put in the real resistance values and it will work. ;)

Lefty! I took a picture of two of them so you wouldn't say that they didn't exist! You mean the color code is wrong?

modeller: You mean the color code is wrong?

Absolutely! All color codes are wrong. I think I smell a conspiracy. Quick someone call Mulder and Scully.

Wait till you see the Zero volt battery I have. 8)

b

JimboZA: Bzzzzzzzzzzzzzzttttt....

1/0 is not infinity, it's undefined.

but infinity is pretty close!

I took a picture of two of them so you wouldn't say that they didn't exist!

It is simply a limitation of the algorithm that the calculator uses. A decent calculator would give you the right answer, however there are very few decent calculators. Ones that don't think a divide by zero is an error. One that had an IEEE maths standard package in it would not blow up. I suspect you are very young if you believe calculators are the arbiters of what is possible in mathematics.

Grumpy_Mike: I suspect you are very young if you believe calculators are the arbiters of what is possible in mathematics.

No, actually I'm 55.

But, now I know why you are called Grumpy Mike. :)

(pssst - it's a joke thread, that's why it's in the Bar Sport board)

it's a joke thread, that's why it's in the Bar Sport board

Yes but it is such a bad joke.

Not as good as the way we used to wind up our purchasing department by insisting that they got 1% zero ohm links in place of the rubbish 5% ones they always bought.

Grumpy_Mike:
Not as good as the way we used to wind up our purchasing department by insisting that they got 1% zero ohm links in place of the rubbish 5% ones they always bought.

Haha! Nice.

Grumpy_Mike:

it's a joke thread, that's why it's in the Bar Sport board

Yes but it is such a bad joke.

Not as good as the way we used to wind up our purchasing department by insisting that they got 1% zero ohm links in place of the rubbish 5% ones they always bought.

And not as good as convincing management to write documents in smaller fonts to save disk space ]:D

modeller:

retrolefty: That was simply a user input error, as there are no zero ohm resistor, certainly not a room temperature. Put in the real resistance values and it will work. ;)

Lefty! I took a picture of two of them so you wouldn't say that they didn't exist! You mean the color code is wrong?

wanna borrow my milliohm meter? you can measure the resistance of pure copper wire with them =)

so he is right, there is no such thing as a zero ohm resistor at room temperature, its resistance is just so freaking tiny it doesnt matter for 99.99999% of applications

Osgeld:
so he is right, there is no such thing as a zero ohm resistor at room temperature, its resistance is just so freaking tiny it doesnt matter for 99.99999% of applications

Man, I shouldnâ€™t have said it was a joke thread, I could have played this out for 20 pages if I had wanted to. LOL.

mmcp42: au contraire 1/r = infinity so R = 0 notaprob

1/r = ALMOST infinity so R = ALMOST 0 :grin: