ohms law

Discussion in 'Math' started by vasdef, Oct 31, 2004.

  1. vasdef

    Thread Starter New Member

    Oct 10, 2004
    I'm a newbie to electronics. I just learned Ohm's law recently, and am having trouble with some of the equations. I don't have any trouble with E=IR, I=E/R, R=E/I, or the
    basic power equation P=EI. It's the other equations that involve square root, and "to the power of" numbers. If someone could direct me to a website to learn this, without having to learn all about algebra, it would be greatly appreciated. I just want to learn enough to use Ohm's law and all the equations. Thanks.
  2. haditya

    Senior Member

    Jan 19, 2004
    algebra is essential
  3. vineethbs

    AAC Fanatic!

    Nov 14, 2004
    right vasdef , r u talking abt the power equations such as e*e/r etc.
    well,u need to know algebra to really do anything anywhere , cuz u have to solve equations etc . Is this ur first course in physics ?
  4. vasdef

    Thread Starter New Member

    Oct 10, 2004

    Never took physics. Took Algebra in 9th grade, but that was 25 years ago. I'm really interested in electronics, and I like math, so I'm willing to learn Algebra. I've got Ohm's
    Law down,and I'm starting to get into the powers and roots now, that's where some of it is a bit confusing to me, for example an equation like: 40=10*I^2

    Maybe you can recommend a book or website. Thanks

  5. vineethbs

    AAC Fanatic!

    Nov 14, 2004
    right , that is the spirit man , the joy of creating something that works is really something .
    Now if u r really interested in practical electronics ,I think u need to know some basic equation solving techniques only .

    in ckt design , the thing that is more important than ohm's law (well, this is based upon ohm's law , but ohms law is experimental , i think , this is more theoritical)

    are the kirchoff's laws , if u r interested then u shud study this too .
  6. ellea

    New Member

    Nov 25, 2004
    Hi vasdef,
    I read your post and I have to say it's students like you who put my spirit up when I feel I'm gonna drop out :)
    Now I'm gonna solve your equation and give you the technique applied to this particular one. But I will look around for books and websites where you can find the info you need and let you know later on.
    Now you have
    40 = 10 * I^2
    now in an equation you are allowed to multiply and divide the two sides by the same number. So let'S say you want to elinimate the 10 you multiply both sides by 1/10 and here's what you get
    40/10 = (10 * I^2)/10
    4 = I^2

    Now with powers it's the same deal. Just a little recall for you
    a^(1/x) is the same as x root of a
    So you can also elevate both sides to the same power:
    4^1/2= (I^2)^1/2
    +/- 4 = I
    now since curent is always a positive value onless it's indicating direction
    you will keep

    I just hope I helped you a bit
    The best of luck with your studies and i'll come back with the info you need :) :)
  7. ellea

    New Member

    Nov 25, 2004
    hey vasdef,

    I didn'T notice but the answer is
    I=2 not I=4
    sorry about that :)
  8. Nirvana

    Well-Known Member

    Jan 18, 2005
    Well as you correctly say to calculate the Power through a component we can use P = VI (or EI as you stated).
    But yes there are two other that are commonly used, these are P = I2 R and P = V2 / R .
    If you look closely at these formulas you might notice something - a similarity perhaps.
    Its ok if you don't I only found it because I was experimenting with the formulas.
    Well you allready know the first formula P = VI, but lets have a look at the second P = I2 R - if we expand this out a bit as we know that I2 = I * I then we get, P = I * I * R,
    and as you no doubt know from ohms law I * R = V, so from the second formula P = I2 R we get P = I * I * R which is P= V I the exact same formula as the first.
    Now what about the third formula, well lets have a look; P = V2 / R now again we know that V2 = V * V.
    So our formula becomes P = V2 / R = V * V /R , look what we have here, we have V/R which again by Ohms Law gives the current I, so all in all we get, P = V2 / R = V * V /R = VI.
    All three power formulas are exactly the same except they are written in a different way.
    Hope That Helps You

    (Please Note that the number 2 in front of a letter is suppose to mean squared, it wouldn't allow me to put squared so I had to put the number 2 instead, sorry for the inconvenience)