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A Level Physics Year 1 > Measurement and Errors > Flashcards

Measurement and Errors Flashcards

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1
Q

What is absolute error?

A

The difference between a measured value and the true value

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2
Q

If the absolute error is a very small number, does that mean it was an excellent experiment?

A

Not necessarily as the error if relative to the size of the measured values

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3
Q

Which has the smallest absolute error, 3.5mg or 3ms^-1?

A

Neither as you can’t compare because they have different units

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4
Q

What is the equation for percentage error?

A

% error = (absolute error / true value) x 100

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5
Q

What unit is percentage error measured in?

A

It has no unit

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6
Q

What can be said about an experiment if the percentage error is as small as possible?

A

The experiment was carried out well

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7
Q

What does an accurate result mean?

A

A result which is close to the true value (has a small percentage error)

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8
Q

What 2 types of error are there?

A

Random error

Systematic error

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9
Q

What is random error?

A

An error that doesn’t follow a consistent pattern

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10
Q

What is an example of a source of random error?

A

Instruments don’t have infinite resolution

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11
Q

What is systematic error?

A

An error that has a consistent pattern

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12
Q

What is an example of a source of systematic error?

A

Incorrect calibration of an instrument (e.g. a micrometre with jaws closed reads 0.02mm so every measurement is 0.02 mm greater)

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13
Q

What is absolute uncertainty?

A

The interval within which the true value is expected to lie

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14
Q

What can you think uncertainty as?

A

The ‘worst case scenario’ estimate of random error

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15
Q

What is the equation for percentage uncertainty?

A

% uncertainty = (absolute uncertainty / measured value) x 100

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16
Q

What is resolution?

A

The smallest division on the scale of an instrument

17
Q

How do you estimate uncertainty using the resolution of the instrument?

A

If the instrument has a resolution of 0.01mm, the uncertainty will always be at least ±0.01 mm

18
Q

What is the best way of estimating uncertainty?

A

Working out ± half the range of repeated measurements

19
Q

What are 3 methods of reducing Random error?

A

Use a measuring device with a higher resolution
Measure a larger quantity
Repeat and average

20
Q

How does using a measuring device with a higher resolution reduce Random error?

A

It can reduce absolute error, and therefore percentage error

21
Q

How does measuring a larger quantity reduce Random error?

A

It will mean that the error is a smaller percentage of the measured value

22
Q

How does repeating and averaging reduce Random error?

A

It helps to spot anomalous results (which can then be removed before averaging)

23
Q

What does repeating and averaging not help with?

A

Reducing systematic error on final values

24
Q

What can you do if you suspect systematic error?

A

Calibrate your apparatus by measuring a known value

25
Q

What does calibration help with?

A

Reducing systematic error as if there’s a difference between your measurement and the known value, you can use this value to correct the inaccuracy

26
Q

What is a zero systematic error?

A

Where an instrument will read a different value when it should be 0

27
Q

How can you see if a graph is directly proportional?

A

If the line of best fit is a straight line that goes through the origin

28
Q

What is a parallax error?

A

An error that occurs because of the angle of view of the observer

29
Q

How can you reduce parallax error?

A

Adjusting the field of view so that the line of sight is perpendicular to the plane of the scale

30
Q

What is the ‘pin and mirror’ technique?

A

A mirror can be used to ensure that the line of sight is perpendicular to the scale

31
Q

What are anomalous results?

A

Results that do not fit the pattern of the rest of the data

32
Q

When adding or subtracting values (with the same units), what do you do with the absolute errors?

A

Add them

33
Q

When multiplying or dividing values (with the same units), what do you do with the percentage errors?

A

Add them

34
Q

When raising a power to the power of n, what do you do to the percentage error?

A

Multiply by n

A Level Physics Year 1 (7 decks)

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