Define random error .

A random error causes unpredictable fluctuations in readings due to uncontrollable factors, such as environmental conditions.

Define systematic error .

A systematic error arises from faulty instruments or a flawed method and is repeated consistently in the same direction every time.

A zero error is a systematic error in which an instrument gives a non-zero reading when the true value is zero .

What is the difference between precision and accuracy?

precision — how close repeated measurements are to each other (small spread) accuracy — how close a measurement is to the true value

Resolution is the smallest change in the quantity being measured that produces a perceptible change in an instrument's reading.

What is the difference between repeatability and reproducibility?

repeatable — the same experimenter repeats the investigation with the same method and equipment and gets the same results reproducible — a different person, or different equipment or technique, obtains the same results

Random errors affect the precision of measurements, whereas systematic errors affect the .......... .

Random errors affect the precision of measurements, whereas systematic errors affect the accuracy .

True or False? Repeating a measurement and averaging reduces systematic error.

False. Repeating and averaging reduces random error. Systematic error is reduced by recalibrating the instrument or correcting the method.

The uncertainty is the range of values around a measurement within which the true value is expected to lie; it is an estimate.

Distinguish absolute, fractional and percentage uncertainty.

absolute — a fixed quantity with the same units as the measurement fractional — the uncertainty as a fraction of the measurement percentage — the uncertainty as a percentage of the measurement

When two quantities are added or subtracted, how are their uncertainties combined?

Add the absolute uncertainties.

When two quantities are multiplied or divided, how are their uncertainties combined?

Add the percentage (or fractional) uncertainties.

When a quantity is raised to a power, its percentage uncertainty is .......... by that power.

When a quantity is raised to a power, its percentage uncertainty is multiplied by that power.

What is the uncertainty in a single reading taken from an analogue scale?

± half the smallest division on the scale.

True or False? The uncertainty in a digital reading is ± the last significant digit, unless stated otherwise.

True. For a digital reading , the uncertainty is taken as ± the last significant digit unless otherwise quoted.

An error bar is a line drawn through a data point on a graph to show the absolute uncertainty in that measurement.

In which direction are error bars usually drawn, and what else can they represent?

Usually vertical , showing the uncertainty in the y-values. They can also be drawn horizontally to show the uncertainty in the x-values.

How do you find the uncertainty in the gradient of a straight-line graph?

Draw a best-fit line and a worst-fit line , then compare their gradients.

Define worst-fit line .

The worst-fit line is the steepest or shallowest possible straight line that still passes within all the error bars.

The best-fit line should pass as .......... to as many of the plotted points as possible.

The best-fit line should pass as close to as many of the plotted points as possible.

True or False? Error bars represent the percentage uncertainty in a data point.

False. Error bars represent the absolute uncertainty in a data point.

A LevelPhysicsAQAFlashcardsMeasurements & Their ErrorsLimitation of Physical Measurements

Limitation of Physical Measurements (AQA A Level Physics): Flashcards

Exam code: 7408

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Define random error.

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Cards in this collection (23)

Define random error.
A random error causes unpredictable fluctuations in readings due to uncontrollable factors, such as environmental conditions.
Define systematic error.
A systematic error arises from faulty instruments or a flawed method and is repeated consistently in the same direction every time.
Define zero error.
A zero error is a systematic error in which an instrument gives a non-zero reading when the true value is zero.
What is the difference between precision and accuracy?
- precision — how close repeated measurements are to each other (small spread)
- accuracy — how close a measurement is to the true value
Define resolution.
Resolution is the smallest change in the quantity being measured that produces a perceptible change in an instrument's reading.
What is the difference between repeatability and reproducibility?
- repeatable — the same experimenter repeats the investigation with the same method and equipment and gets the same results
- reproducible — a different person, or different equipment or technique, obtains the same results
Random errors affect the precision of measurements, whereas systematic errors affect the ...........
Random errors affect the precision of measurements, whereas systematic errors affect the accuracy.
True or False?
Repeating a measurement and averaging reduces systematic error.
False.
Repeating and averaging reduces random error. Systematic error is reduced by recalibrating the instrument or correcting the method.
Define uncertainty.
The uncertainty is the range of values around a measurement within which the true value is expected to lie; it is an estimate.
Distinguish absolute, fractional and percentage uncertainty.
- absolute — a fixed quantity with the same units as the measurement
- fractional — the uncertainty as a fraction of the measurement
- percentage — the uncertainty as a percentage of the measurement
How do you find the uncertainty in the mean of a set of repeated readings?
Take half the range:
$uncertainty = \frac{1}{2} (largest - smallest)$
When two quantities are added or subtracted, how are their uncertainties combined?
Add the absolute uncertainties.
When two quantities are multiplied or divided, how are their uncertainties combined?
Add the percentage (or fractional) uncertainties.
When a quantity is raised to a power, its percentage uncertainty is .......... by that power.
When a quantity is raised to a power, its percentage uncertainty is multiplied by that power.
What is the uncertainty in a single reading taken from an analogue scale?
± half the smallest division on the scale.
True or False?
The uncertainty in a digital reading is ± the last significant digit, unless stated otherwise.
True.
For a digital reading, the uncertainty is taken as ± the last significant digit unless otherwise quoted.
Define error bar.
An error bar is a line drawn through a data point on a graph to show the absolute uncertainty in that measurement.
In which direction are error bars usually drawn, and what else can they represent?
Usually vertical, showing the uncertainty in the y-values. They can also be drawn horizontally to show the uncertainty in the x-values.
How do you find the uncertainty in the gradient of a straight-line graph?
Draw a best-fit line and a worst-fit line, then compare their gradients.
Define worst-fit line.
The worst-fit line is the steepest or shallowest possible straight line that still passes within all the error bars.
How is the percentage uncertainty in a gradient calculated?
$% uncertainty = \frac{| best gradient - worst gradient |}{best gradient} \times 100 %$
The best-fit line should pass as .......... to as many of the plotted points as possible.
The best-fit line should pass as close to as many of the plotted points as possible.
True or False?
Error bars represent the percentage uncertainty in a data point.
False.
Error bars represent the absolute uncertainty in a data point.

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