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Rev. Notes > AS > Measuring techniques
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Measurements Errors Random error
Systematic error Uncertainty Total uncertainity in addition / subtraction
Total uncertainty in multiplication and division Total uncertainty in power factor Total uncertainty in the average value of many measurements
Total uncertainty in the timing experiment Total uncertainty in the timing experiment Example 1 - Calculation of uncertainty
Least count Spring Balance Digital Balance
Protractor Micrometer Vernier calliper
Digital Ammeter Cathode Ray Osciloscope

Total uncertainty in multiplication and division

Percentage uncertainties are added. For example the maximum possible uncertainty in the value of resistance R of a conductor determined from the measurements of potential difference V and resulting current flow I by using R = V/I is found as follows:
                                    V = 5.2 ± 0.1 V
                                    I = 0.84 ± 0.05A
The %age uncertainty for V is =(0.1 V / 5.2 V)  X (100 / 100) = about 2 %
The %age uncertainty for I is = (0.05 A / 0.84 A) X (100 / 100) = about 6 %
Hence total uncertainty in the value of resistance R when V is divided by I is 8%. The result is thus quoted as
R =  = 6.19 VAˉ¹ = 6.19ohms with a %age uncertainty of 8%
that is                           R = 6.2 ± 0.5 ohms
The result is rounded off to two significant digits because both V and R have two significant figures and uncertainty, being an estimate only, is recorded by one significant figure.

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View Comments on this Chapter - Total Comments (4)
Yunzila Said :
but we have calculated the value with the given radius then what is the need of division by 2......???
  07/12/17 12:21 PM
Yunzila Said :
why in the ans is 0.6.......??? bcz after calculation we get 1.2.....!!!
  07/12/17 12:17 PM
unknown Said :
^to calculate the radius, diameter needs to be divided by 2. thus, 1.22/2 = 0.61
  02/01/15 12:33 AM
Bilal Said :
where did 0.6 come from in result
  09/09/14 02:51 PM


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