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Branch current issues

Discussion in 'General Electronics Discussion' started by Chickwolf, Jan 3, 2014.

  1. Chickwolf

    Chickwolf

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    Jan 3, 2014
    Hello all, first post here so be gentle ;)

    Basically by problem is that im trying to work out the current in the branches of the circuit. I understand that the branch current should be the supply voltage divided by the total branch resistance (I= V/R) but every time I try that and add both branch together to get the total current of the circuit, its coming out at twice as much as it should be. I worked out the total current to be 50mA but when I work out the branch currents and add them together, it gives me a total of 100mA. Any useful bits of information would be greatly appreciated.

    Chick.
     

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  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Is this homework?

    You're correct that 50mA flows out of the battery (49.97mA).

    So which resistors have 50mA flowing through them?

    Of the other resistors, what can you say about the current?

    Can you calculate the voltage across R1?

    Can you calculate the voltage across R6?

    Can you calculate the voltage across R5?

    What does this allow you to do?
     
  3. Chickwolf

    Chickwolf

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    Jan 3, 2014
    Just a bit of spare work I had lying round from college, thought I would give it a go.
    50mA of current would be flowing through R1 and R6 as they are in series. But the current would split to go through the separate branches of of the parallel resistors.
    The voltage across the resistors would be:
    R1= 2
    R5= 4.5
    R6= 3.5
    I'm not to sure how to proceed from this point...
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Can you determine the current through R5 now?
     
  5. Chickwolf

    Chickwolf

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    Jan 3, 2014
    Suddenly realized how obvious that was now, thank you for pointing that out!
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,214
    2,695
    Jan 21, 2010
    Glad to have helped you with an "a-ha!" moment. :)
     
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