Topic 1 : Measurement and Uncertainties Flashcards Preview

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Flashcards in Topic 1 : Measurement and Uncertainties Deck (23)
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1
Q

Temperature SI Unit

A

Kelvin (K)

2
Q

Distance SI Unit

A

Meters (m)

3
Q

Current SI Unit

A

Ampere (A)

4
Q

Time SI Unit

A

Second (s)

5
Q

Amount of Substance SI Unit

A

Mole (mol)

6
Q

Mass SI Unit

A

Kilogram (kg)

7
Q

Light Intensity SI Unit

A

Candela (cd)

8
Q

Derived quantities

A
  1. Derived quantities have units that are combinations of the fundamental units
  2. e.g. speed (m/s) or acceleration (m/s)
9
Q

Analog measuring device vs Digital measuring device

A

analog measuring device is where you have to estimate last digit, somewhere between 2 digits whereas digital measuring device gives an exact last digit

10
Q

Accuracy

A

how close an experimental value is to the true value

11
Q

Uncertainty

A

used to estimate the likely ranges in which the true value will lie

12
Q

Random error

A
  1. error due to the person measuring, rather than the instrument
  2. affects the precision of the reading
13
Q

Random Uncertainties

A
  1. Random uncertainties/errors occur in any measured quantity
  2. The more measurements are taken, the closer the mean value of the measurements is likely to be to the “true” value of the quantity
  3. Taking repeat readings and calculating an average → reduces the effect of random uncertainties, improves the accuracy of the results
14
Q

Parallax error

A

eye viewing meniscus at an angle rather than eye-level with the reading and perpendicular to the scale

15
Q

Systematic error

A
  1. due to the instrument “out of adjustment” or poorly calibrated (e.g. voltmeter having a zero offset error or meter stick rounded on one end)
  2. affects the accuracy of the reading
  3. Taking repeats using the same method does not reduce systematic errors
16
Q

Absolute error

A

raw uncertainty / precision of measurement → smallest unit of measurement of instrument

17
Q

To calculate uncertainty for repeated measurements

A

absolute uncertainty = (max-min)/2

18
Q

fractional error formula

A

fractional error = absolute error/measured value

19
Q

percentage error formula

A

percentage error = (absolute error/measured value) * 100%

20
Q

Calculating uncertainty in sum / difference

A
  1. To find the uncertainty in a sum, add the uncertainties of all the terms in the sum/difference
  2. If y = a±b, then Δy = Δa + Δb
21
Q

Calculating uncertainty in product / quotient

A
  1. To find the uncertainty in a product or a fraction, add the percentage or fractional uncertainties of all the ingredients to find the total percentage or fractional uncertainty in the calculated value
  2. If y = (ab) / c, then Δy / y = Δa/a + Δb/b + Δc/c
22
Q

Scalar

A

quantity that has only magnitude (size)

23
Q

Vector

A

quantity with a magnitude (size) and a spatial direction