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Thread: voltmeter

  1. #1 voltmeter 
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    i have a voltmeter, and noticed, waving around the pins in the air seemed to generate a small voltage, in the order of 2.5mV
    waving it around a magnet, seemed to generate about 20mV.
    whats this?


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  3. #2  
    Administrator KALSTER's Avatar
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    the magnet induces a current in the voltmeters wires. are you touching the red and black contact points together?


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  4. #3  
    Forum Masters Degree bit4bit's Avatar
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    The effect is most likely the result of a small current being induced in some part of the voltmeter circuit, producing an observable voltage when moved through the earths magnetic field. (similar to an electrical generator)

    The effect will be greater when moved through the field of a permanent magnet, because at close proximity, the magnetic field (and hence induction) will be relatively higher.
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  5. #4  
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    it only works if you wave it, though. the fieldlines have to be in flux through the loop.
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

    "Gullibility kills" - Carl Sagan
    "All people know the same truth. Our lives consist of how we chose to distort it." - Harry Block
    "It is the mark of an educated mind to be able to entertain a thought without accepting it." - Aristotle
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  6. #5  
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    Your digital voltmeter has a very high input impedance and will pick up a lot of stray voltage, noise really, that the old style galvanometer voltmeters won't. There is not any real energy to it and the voltage is basically shorted out through the galvanometer windings of the old style voltmeters.

    The voltage generated by moving a conductor near a magnet is according to Faraday's law.

    I assume your meter is set to the d-c millivolt scale. Most meters don't read a-c voltages that low. That being the case, my guess is that the voltage you measure without the magnet present could be just be static electrical fields capacitively coupled to your meter leads.
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  7. #6 Re: voltmeter 
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    Quote Originally Posted by dejawolf
    i have a voltmeter, and noticed, waving around the pins in the air seemed to generate a small voltage, in the order of 2.5mV
    waving it around a magnet, seemed to generate about 20mV.
    whats this?
    Your need to talk to a scientific parent.
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  8. #7  
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    yeah, its d.c.
    when you have eliminated the impossible, whatever remains, however improbable, must be the truth
    A.C Doyle
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    nO.
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