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Homework Help: Resistor Help

  1. Jun 1, 2008 #1
    1. The problem statement, all variables and given/known data
    2ohms 4ohms 3ohms and 9ohms are connected across an 8-V DC source. what is the current through the 9ohm resistor

    Another problem is

    A 100 V DC signal is applied to four resistors. the values of the resistors are 20ohm 40ohm 60ohm and 80ohm. what is the voltage across the 40 ohm resistor.

    They're kind of similar except one is current the other is voltage.

    2. Relevant equations
    i don't know

    3. The attempt at a solution

    i don't know.
  2. jcsd
  3. Jun 1, 2008 #2
    Remember that ohms are a measure of resistence, whereas voltage is the max flow under zero resistance. What you need to do is see how much electricty is lost as it passes through each resistor.
  4. Jun 1, 2008 #3


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    So... you haven't seen any examples of someone solving for quantities in a circuit given other quantities? And you haven't been taught any formulae relating current, voltage, and resistance? If so, then the best way to proceed would be to complain to your school's science department.
  5. Jun 1, 2008 #4
    How do I find out how much is lost through each resistor.
  6. Jun 1, 2008 #5
    Doesn't your school provide you with text books? The methods should be listed in plain language. I could just blurt out the method, but it's important to be able to use your text books / library to get the information you need.
  7. Jun 1, 2008 #6
    Can you just show me how this is done because I have no clue whatsoever and showing me how this is done will allow me to do the problems that follow.
  8. Jun 1, 2008 #7


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    Can, yes. Will, no. We have an explict policy on physics forums that we will not do your homework for you.
  9. Jun 1, 2008 #8
    It's just one problem so I see how to it and then I can do the rest.
  10. Jun 1, 2008 #9
    You're being given Voltage and Ohms, you need to find Amperage. Research formula which relate the three measurements. If you learn how they are related, and what Ohms/Amps/Volts are, the solution will become apparant.
  11. Jun 1, 2008 #10
    So is the answer for the first one just going to be 8/9?
  12. Jun 1, 2008 #11
    And the other one 100volts. That doesn't make any sense to me.
  13. Jun 1, 2008 #12
    What do parallel and series look like? And are you sure you're supposed to add the resistors together?
  14. Jun 1, 2008 #13
    What book are you using?
    Are these questions from that textbook?
    Have you read the chapters covering ohms law and simple circuits?

    Look at the examples, get some idea of what you need to do.
    Otherwise all anyone will be able to do is solve these for you.
    That will harm you not help you.
  15. Jun 1, 2008 #14
    It's a studyguide for the final.
  16. Jun 1, 2008 #15
    Ok, a study-guide. Do you have a resource available besides the study-guide?
  17. Jun 1, 2008 #16
    My textbook.
  18. Jun 1, 2008 #17
    Good, now we can make some progress. What textbook?
  19. Jun 1, 2008 #18
  20. Jun 1, 2008 #19
    OK, look in chapter 21 ( I think) it covers electric current and direct current circuits.

    Edit: post again when you have found the correct chapter. There are some examples we can discuss.
    Last edited: Jun 1, 2008
  21. Jun 1, 2008 #20
    Yeah I was looking at 21-2
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