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Thread: series and parallel

  1. #1 series and parallel 
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    Now my question is extremely simple, but i just can't grasp the idea, so hopefully someone can help.

    In a series cicuit when 2 bulbs are connected, they will glow less bright than when only one bulb is connected.
    When 2 bulbs is connected in parallel, both bulbs glow as brightly as when only one bulb is connected.

    I don't understand why this happens. In a parallel circuit the current is split between the two paths, and so there is less current through each bulb, so why does the bulbs glow more brightly than when they are connected in series?


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  3. #2  
    Forum Isotope Zelos's Avatar
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    becuase there is less resistence when they are connected parralell.
    and also the voltage is the same on both of them
    IR=U
    P=IU
    I=U/R
    P=U²/R
    The voltage dont drop and the resistence is slithly less therefor is it a bit brighter, i think
    1/R<sub>Tot</sub>=1/R<sub>1</sub>+1/R<sub>2</sub>......1/R<sub>n</sub>


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  4. #3  
    Forum Professor wallaby's Avatar
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    Quote Originally Posted by Zelos
    IR=U
    P=IU
    I=U/R
    P=U²/R
    The voltage dont drop and the resistence is slithly less therefor is it a bit brighter, i think
    1/R<sub>Tot</sub>=1/R<sub>1</sub>+1/R<sub>2</sub>......1/R<sub>n</sub>
    you should know that those symbols just mean so much to people like me who havn't seen them before.
    may i ask what these letters I, R, U and P represent.
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  5. #4  
    Forum Professor Zwolver's Avatar
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    U = Voltage in Volts

    I = Current in Amps

    R = Resistance in Ohm

    P = Power in Watt

    And the reason it burns less is that the amount of amps is divided in 2.
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  6. #5 Re: series and parallel 
    Forum Radioactive Isotope mitchellmckain's Avatar
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    Quote Originally Posted by chocolate123
    Now my question is extremely simple, but i just can't grasp the idea, so hopefully someone can help.

    In a series cicuit when 2 bulbs are connected, they will glow less bright than when only one bulb is connected.
    When 2 bulbs is connected in parallel, both bulbs glow as brightly as when only one bulb is connected.

    I don't understand why this happens. In a parallel circuit the current is split between the two paths, and so there is less current through each bulb, so why does the bulbs glow more brightly than when they are connected in series?
    I think your difficulty arises from thinking of the current as independent of how you put the light bulbs in the circuit. This is different from water in a river where the current is fixed and is independent of how you divide the streams of water, unless you think of the light bulbs as floodgates in a dam which allow only a percentage of the current through. If you open two flood gates in two damns in parallel streams you get exactly the same water flowing through as one damn. But with two in series you get much less water flowing through.
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  7. #6  
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    thanks for the replies. i kinda think i get some of it.
    So i suppose there is half the amount of current in each path in a parallel cirucuit, but the current passing through the 2 bulbs are the same as the current passing through one in a series circuit, because the bulbs only allow a certain amount of current through.
    By the way P=VI so shouldnt power be less (since current is halved)?
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  8. #7  
    Forum Freshman SinMan's Avatar
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    chocolate,

    Connecting the 2 bulbs in parallel demands for twice power (in Ampere) as delivered if only one bulb was connected because the resistance (R) is halved when we replace the series by parallel since I=U/R.
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  9. #8 Re: series and parallel 
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    Quote Originally Posted by chocolate123
    In a parallel circuit the current is split between the two paths, and so there is less current through each bulb, so why does the bulbs glow more brightly than when they are connected in series?
    You are assuming there is a fixed amount of current available here ie a constant current source - in which case the current would be split two ways.
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