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Question regarding electric circuits and current

  1. Nov 16, 2012 #1
    1. The problem statement, all variables and given/known data

    electric_circuits.jpg

    Referring to the electric circuit above, when the switch(S) turn on, the brightness bulb Q and Ammeter reading increases. so my question is, why? is it true that the S create another path way for current, then at the end of S, the electric current joins the electric current passed through bulb P , so the brightness of bulb Q increase? and why is the ammeter reading increase? Please correct me if my concept is wrong, thanks in advance.

    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Nov 16, 2012 #2

    phinds

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    Do you understand how current flows in a circuit? Do you understand the relationship between resistance and current?
     
  4. Nov 16, 2012 #3
    As how the current flows in a circuit, I am not that certain, but for the relationship between resistance and current, I understand it with the help of ohm's law
     
  5. Nov 16, 2012 #4

    phinds

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    Good. THen how about you think of a better way of saying
    and think about what that means for the current in the circuit.
     
  6. Nov 16, 2012 #5
    Sorry but, I don't get it.. :confused:
     
  7. Nov 16, 2012 #6
    I just went through some reference book, and i got a conclusion. Correct me if i am wrong. The the switch S is closed, the current doesn't flow through P anymore, instead they only flow through the pathway S, as a result, the current doesn't undergo any resistance, and hence, the total Current is greater. In terms of equation, the resistance of S is negligible, so the effective resistance = 1/P + 1/0.00000000...... , and the resultant resistance is very small. Am I right?
     
  8. Nov 17, 2012 #7

    phinds

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    Yes, the bolded part is what I wanted to make sure you understand because this is what makes the total circuit resistance lower. As for specifics, I don't see any values on your diagram.
     
  9. Nov 17, 2012 #8
    Okay I finally got it, THANK YOU VERY MUCH DUDE !! :biggrin:
     
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