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Homework Help: Help with phisics

  1. Sep 10, 2009 #1
    Hey guy! im new here and im seeking some help!
    so i just started a Electric Engineering course at grimsby collage and, i thought i had some sceince knowlage ohms and that. ya know? untill they gave me this.

    Calculating Resistor Values.
    Two Resistors are connected in series with values of 220ohm & 390ohm


    Two Resistors are connected in series with values of 1k2ohm & 2k2ohm

    im not askin u to tell me the answer. just how grasp and work out the equasion.

    i kinda just jumped in at the deep end without any know-how. one year a plumber, next an engineer.
  2. jcsd
  3. Sep 10, 2009 #2
    If you expect to really receive some help, then show your work. If you don't know how to calculate the total resistance then take a look http://http://en.wikipedia.org/wiki/Resistor" [Broken], though your textbook (if you have one) should have all the information since this is a basic question.
    Last edited by a moderator: May 4, 2017
  4. Sep 10, 2009 #3
    Two resistors in series have the same current through them.

    So using ohms law (V = iR) [tex]V_{total} = iR_1 + iR_2 = i(R_1+R_2)[/tex]

    So as you can see an equivalent resistor would just the from the addition of the two resistors.
  5. Sep 10, 2009 #4


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    Gold Member

    Dumb question, but is Ohm's law considered a formulation in algebra, physics, etc?
    Good info on this article, and I have been reading through this forum trying to absorb some info for my own school start, but I am 15-years out of high school and I don't remember alot/any of this.
  6. Sep 10, 2009 #5


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    Staff: Mentor

    Welcome to the PF. Not really a dumb question, but I'm afraid I don't quite understand what you are asking. Ohm's law is just an algebraic relationship between current, voltage and resistance (or more generally impedance, when you get to complex number representations). There are reasons in physics behind the algebra, however. Hope that helps some...
  7. Sep 14, 2009 #6
    ok, thanks guys i still dont fully undersatand but i kinda get the equasion. please correct me if im wrong.
    so (V = iR) so V is voltage? I - currrent, and R is resistance.
    (V=iR) Vtotal = iR1 + iR2 = i(R1 + R2)
    so ir1,2 are the phases the currents split off into ect.
    just thinking out loud.. V x I = R. (multipling 2 to find the 3rd also works?)
    also ive been reading up on this, starting to make sense.
    but i still dont know what ohms law is.... anyone have an link to some info
    would be great!

    Tony :)
  8. Sep 14, 2009 #7


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    Staff: Mentor

    Here's an intro link:


    You should also read up on Series and Parallel connections of resistors, to better understand how the currents divide, and how the voltages add up.
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