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Thread: Negative Voltage?

  1. #1 Negative Voltage? 
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    Hey Guys,

    I have been wondering about this for quite some time, when a voltage is considered to be negative does that mean
    the "Ground" is positive with respect to it and thus current flows from "Ground"?

    For example i had -5v and 5v, current would flow from 5v to ground, with -5v current would flow from ground to -5v?

    Sorry if this is a dumb question,

    Thanks


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  3. #2  
    Forum Bachelors Degree One beer's Avatar
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    Yes, basically you have it right. Compared to a minus voltage, ground is positive. Voltages are also known as potential differences, so your -5 volts is a negative pd compared to ground, but it would be positive pd compared to -10 volts.


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  4. #3  
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    So just to clarify, current would flow from ground to -5v, and current would flow from -5v to -10v?
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  5. #4  
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    Quote Originally Posted by James1993 View Post
    So just to clarify, current would flow from ground to -5v, and current would flow from -5v to -10v?
    Conventional current would, yes. However, the actual electron flow goes in the opposite direction.

    Basically, what happened is that when Franklin was studying electricity, he assumed it was due to some thing that flowed from a surplus (+) to a deficit(-). However he had no way of knowing which direction this flow went. So he picked one terminal and labeled it (+).

    Much later we learned that the actually mediators of the current were electrons, which flowed in the other direction. By this time, the +/- convention was firmly in place. Both current directions are still taught today, and it really doesn't matter which one you use, as long as you remain consistent.
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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  6. #5  
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    There is nothing magical about "ground" - it is just a point of reference. To make an analogy with gravity, you could say your back yard is "ground" and anything higher than your back yard is at a positive elevation, so it will flow toward ground. But if your neighbor's back yard is at a lower elevation than your own, it would have a negative elevation. Would the water flow from "ground" to negative? Yep.
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  7. #6  
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    Yep, I agree. Both good points.
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  8. #7  
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    Okay cool, I'm pretty sure I understand it now.

    Cheers
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