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    hello there

    I am doing my ASlevel coursework piece on the EMF and internal resistance of a cell.

    I have some results which I have got from another source which include the uncertainty in volts and the voltage measurement. I have been told the ABSOLUTE uncertainty in the volt meter is+/- 0.01v and the % uncertainty is 2%


    How do I get the uncertainty values in that column? (B) thanks

    PICTURE:Name:  uncertainty.png
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    EDIT: In column B all the values should have "+/- " in front of them
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    Okay lets say I am using a voltmeter which has an absolute uncertainty of +/-0.01v and a percentage uncertainty of +/-2%

    I then take a reading using that voltmeter and get the reading to be 1.36v

    What would the uncertainty be in the reading? thanks. Would it be +/- 0.03? The answer book says it is but I don't know how to get that. Thanks
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    (Original post by upthegunners)
    hello there

    I am doing my ASlevel coursework piece on the EMF and internal resistance of a cell.

    I have some results which I have got from another source which include the uncertainty in volts and the voltage measurement. I have been told the ABSOLUTE uncertainty in the volt meter is+/- 0.01v and the % uncertainty is 2%


    How do I get the uncertainty values in that column? (B) thanks

    PICTURE:Name:  uncertainty.png
Views: 61
Size:  9.2 KB

    EDIT: In column B all the values should have "+/- " in front of them
    The values in that column look like the absolute uncertainty corresponding to a percentage uncertainty of 2%
    Without any further details about how these measurements were performed it's not possible to say much more.
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    (Original post by upthegunners)
    Okay lets say I am using a voltmeter which has an absolute uncertainty of +/-0.01v and a percentage uncertainty of +/-2%

    I then take a reading using that voltmeter and get the reading to be 1.36v

    What would the uncertainty be in the reading? thanks. Would it be +/- 0.03? The answer book says it is but I don't know how to get that. Thanks
    This question is related to the one you already have in the other thread on uncertainty.
    I've moved it there.
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    (Original post by Stonebridge)
    The values in that column look like the absolute uncertainty corresponding to a percentage uncertainty of 2%
    Without any further details about how these measurements were performed it's not possible to say much more.
    thanks for moving it

    I basically just had a series circuit connect up to a 1.5v cell, rheostat and ammeter and took 10 voltage readings a difference resistances and that's it
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    (Original post by upthegunners)
    Okay lets say I am using a voltmeter which has an absolute uncertainty of +/-0.01v and a percentage uncertainty of +/-2%

    I then take a reading using that voltmeter and get the reading to be 1.36v

    What would the uncertainty be in the reading? thanks. Would it be +/- 0.03? The answer book says it is but I don't know how to get that. Thanks
    There are two things going on here.
    Firstly the ± 0.01V is the precision of the instrument. This is the smallest division on its scale. This value is not necessarily the uncertainty in a reading taken with that instrument.

    % uncertainty is the actual uncertainty divided by the value of the reading and times 100
    So if you have 1.00 ±0.01V that is a % uncertainty of 1% for example.

    (0.01/1.00) x 100

    If, on the other hand, you are told that an instrument has a % uncertainty in all readings of, say, 2% then each reading will be ± 2%
    so if you have a reading of 2.00V the uncertainty will be ± 0.04V
    This is because 0.04 is 2% of 2.00
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    (Original post by Stonebridge)
    There are two things going on here.
    Firstly the ± 0.01V is the precision of the instrument. This is the smallest division on its scale. This value is not necessarily the uncertainty in a reading taken with that instrument.

    % uncertainty is the actual uncertainty divided by the value of the reading and times 100
    So if you have 1.00 ±0.01V that is a % uncertainty of 1% for example.

    (0.01/1.00) x 100

    If, on the other hand, you are told that an instrument has a % uncertainty in all readings of, say, 2% then each reading will be ± 2%
    so if you have a reading of 2.00V the uncertainty will be ± 0.04V
    This is because 0.04 is 2% of 2.00
    thanks sooo much dude! You're explained that better than my teacher

    And he also did say that the +/-1.00 was in fact the uncertainty
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    (Original post by Stonebridge)
    There are two things going on here.
    Firstly the ± 0.01V is the precision of the instrument. This is the smallest division on its scale. This value is not necessarily the uncertainty in a reading taken with that instrument.

    % uncertainty is the actual uncertainty divided by the value of the reading and times 100
    So if you have 1.00 ±0.01V that is a % uncertainty of 1% for example.

    (0.01/1.00) x 100

    If, on the other hand, you are told that an instrument has a % uncertainty in all readings of, say, 2% then each reading will be ± 2%
    so if you have a reading of 2.00V the uncertainty will be ± 0.04V
    This is because 0.04 is 2% of 2.00
    sorry to hassle you again but how would I calibrate the voltmeter?
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    (Original post by upthegunners)
    sorry to hassle you again but how would I calibrate the voltmeter?
    There are a number of ways.
    It depends on
    - what type of voltmeter it is
    - what equipment you have at your disposal

    I imagine your teacher would help you with this.

    Try Googling
    "Weston Cell" for a start.
 
 
 
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