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Physics > Measurements and Errors > Flashcards

Measurements and Errors Flashcards

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1
Q

What is accuracy?

A

How close the results are to the true value.

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2
Q

What is precision?

A

How close each data point is together (variance).

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3
Q

What is error?

A

The uncertainty due to the measuring instrument (difference between measured and expected value).

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4
Q

What is random error?

A

Refers to random fluctuations in the measured data.

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5
Q

State three factors which could cause a random error.

A

The readability of the instrument, the effects of something changing in the surroundings between measurements and the observer making a mistake.

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6
Q

What is a systematic error?

A

Refers to reproducible fluctuations consistently in the same direction.

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7
Q

State three factors which could cause a systematic error.

A

An instrument being wrongly calibrated, An instrument with a zero error and the observer making the same mistake in every reading.

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8
Q

How do you correct for a zero error?

A

The value when it should be zero should be subtracted from every reading.

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9
Q

How can you reduce random error.

A

Take repeat measurements (at least three).

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10
Q

How can you reduce systematic error?

A

Calibrate the measuring instrument by measuring a known value. e.g. measure a 1kg mass on scales.

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11
Q

How should water level in a tube be measured?

A

From the lowest point and in the middle of the meniscus (the dip in the water).

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12
Q

What is parallax error?

A

Taking an incorrect reading from the measuring instrument due to taking the reading from an angle other than directly in-line.

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13
Q

What is uncertainty stated as?

A

Plus or minus the least count (smallest value).

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14
Q

What is the uncertainty on a ruler?

A

Plus or minus 0.1cm

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15
Q

What is the uncertainty of a stopwatch?

A

Plus or minus 0.3s due to taking human reaction times into account. (This must be clearly stated if done)

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16
Q

What is the difference between a reading and a measurement?

A

A reading where the zero is assumed to be correct such as with a thermometer but a measurement is where the zero is manually placed such as with a ruler.

17
Q

What is the uncertainty for readings?

A

Plus or minus half the smallest value.

18
Q

What is the uncertainty for measurements?

A

Plus or minus the smallest value.

19
Q

How would you state the resistance of a lamp given some data points?

A

The resistance of the lamp is the mean plus or minus half the range. Anomalous data points aren’t included in finding the mean or range.

20
Q

How do you work out percentage uncertainty?

A

((Approximate value - Exact value) / Exact value) x 100 or (Absolute uncertainty / recorded value) x 100

21
Q

What should be done if an equation is used which introduces new terms which weren’t mentioned in the question?

A

Define the terms of the equation.

22
Q

What is a vernier calliper?

A

A measuring instrument capable of more precise readings.

23
Q

What do more precise readings from a vernier scale do?

A

Reduce systematic error.

24
Q

What type of error is a parallax error?

A

Random error.

25
Q

How can you reduce the uncertainty of a measurement of the width of a constantan wire?

A

Measure the width in an odd number amount of places randomly along the wire and calculate an average.

26
Q

What is the resolution of a voltmeter?

A

0.01V

27
Q

What is the resolution of an ammeter?

A

0.01A

28
Q

What is the resolution of a micrometer?

A

0.01mm

29
Q

What is the resolution of a 30cm ruler?

A

1mm

30
Q

How can the heating effect be reduced when measuring the resistivity of a wire?

A

Take the length measurements from longest to shortest and switch off the current between readings.

31
Q

How do you deal with errors worked out from equations with powers?

A

Multiply the error by the power.

32
Q

State four safety considerations for the resistivity in the constantan wire experiment.

A

Don’t touch the wire when it is hot or there is current flowing, switch off the power if you smell burning, switch off the power between readings and wear safety goggles.

33
Q

What is the value of the prefix: Pico?

A

x10^-12

Physics (14 decks)

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