question on hipass or low freq.calculations

[donald stringer]

The formula f=1/2xpi[3.14]xRxC    I can do this, but my question is how do I know where to place the decimal point. Here is an example:   R=10k[would I write this as 10000 ]? C=.1 [this would be written as .1]?       2x3.14=6.28 Am I correct so far?   6.28x10000=62800     62800x.1=6280     1 / by6280= .000159236     freq=.000159236 Here is my question again, how do I know how many places to count over for the decimalpoint to be placed in the correct position.  One more question  if I were calculating R as 1 meg would I write it as 1,000,000    This is much more simple than I am making it but as much as math interests me it is also a challeng.

[Seljer]

You have to get it into the standard units so it comes back at you in regular hZ

.2microfarads = 2*10^-7 farads

1kohm = 1*10^2 ohms


lately I've been lazy and just let google do everything http://www.google.com/search?hl=en&q=1%2F%282*pi*0.0082microfarads*1kiloohms%29&btnG=Google+Search

[donald stringer]

Thank a lot, by the way what does this symbol mean   ^   

[donald stringer]

google to the rescue    It means to the power of right?     so 1k=1x10 to the second power

[Seljer]

google to the rescue    It means to the power of right?

yep , since regular keyboard characters can't do all those fancy symbols unfortunatley

[burnt fingers]

Man you can google anything these days.  

[Seljer]

Man you can google anything these days. 

My favourite one :
http://www.google.com/search?hl=en&q=the+answer+to+life%2C+the+universe+and+everything&btnG=Google+Search

[donald stringer]

from microfarads to farads .2mf=2x10 to the power of -7 [what is negative 7]?

[Seljer]

from microfarads to farads .2mf=2x10 to the power of -7 [what is negative 7]?

it was ^-7 because it was 0.2 at the start, not 2 and I just added that one in with the rest of them


milli = 10^-3 (or 0.001)
micro = 10^-6 (or 0.000001)
nano = 10^-9 (or 0.000000001)
pico = 10^-12 (you get the idea)
and I can't remember anything smaller than that

[Transmogrifox]

...what is negative 7?

For exponents, here's how it works:

x^n,

When "n" is a positive number, then it means x*x*x*x...., "n" number of times.
For example, 2^6 means,
2*2*2*2*2*2

"n" can be any number, though.  "n" could be 0 or -6.  I'm going to start with an interesting illustration to put a little more light on the topic:

By means of an example, we could use 2^6:

2*2*2*2*2*2 = (2*2*2)*(2*2*2) = (2^3)*(2^3) = 2^(3+3) = 2^6

Why did I do that funny redundant thing with math?  This was to illustrate that (x^n)*(x^m)= x^(m+n), and more simply put, exponents add when two terms with the same base are multiplied together. Let's take another example:

Based on the above,
(2^5)*(2^-3) = 2^2 = 4
also,
(2^5)/(2^3) =32/8=4

For you mathematically minded people, I just need to state this is not intended to be a mathematical proof, but simply an illustration to show why exponents are expressed this way.

I'll simply state these two properties based on the above suggestions (you can find them rigorously proven in mathmatics texts if you need the proof, but this is stuff that you'd learn in any basic algebra class):


(x^n)*(x^m)= x^(n+m),
and
(x^n)/(x^m)= x^(n-m),

So we can re-write any exponent in this form:

(x^n)/(x^m)

For example, 2^2 can be written as (2^7)/(2^5)=2^(7-5) = 2^2
We can also do this:
(2^7)/(2^7)=2^(7-7) = 2^0

And that's twist I was trying to get on this.

Anything to the 0 power is 1.

So 10^(-6) can be rewritten as (10^0)/(10^6).  Ha!

So the answer to your question about what is the "-7" :

It just means 1/(10^-7).  When you see a minus power, it just means 1 divided by the number to that power.  Another way to think about it with powers of 10 is that it just reverses the direction that you move the decimal point.  If it's a positive exponent, you move the decimal point to the right by that many places.  If it's negative, you move the decimal point left that many places:

(1.0)* 10^(-6)
=0.000001

As you can see, the decimal point was just moved 6 places to the left.

Did that help put together the big picture?

[donald stringer]

Yes