Uncertainities

Question 1

What is our uncertainty when using an instrument?

Answer 1

The resolution of the instrument (the smallest possible measurement)

Question 2

What is the uncertainty in a spread of reading?

Answer 2

Range
———
2

Question 3

How do we calculate % uncertainties?

Answer 3

Estimated uncertainity
———————————- x 100
Mean value

Question 4

Which uncertainties are always added - absolute or % uncertainties?

Answer 4

% uncertainties

Question 5

What’s the % uncertainties when multiplying and/or dividing quantities?

Answer 5

Add the % uncertainties of the different quantities

Question 6

What’s the % uncertainty when multiplying by a constant?

Answer 6

Unchanged

Question 7

What’s the % uncertainty when a quantity is raised to a power?

Answer 7

Multiplied by the same power

Question 8

To how many significant figures is uncertainty always quoted to?

Answer 8

1

Question 9

How do we know which value has contributed most to an uncertainty?

Answer 9

Highest percentage uncertainty

Question 10

What is there never any uncertainty in?

Answer 10

Numbers or constants

Question 11

How many significant figures are used for % certainties?

Answer 11

No more than 2 significant figures

Question 12

How many significant figures have to be used for solute uncertainties every time?

Answer 12

1

Question 13

What do you have to do once you’ve changes the significant figure of the absolute uncertainty to be 1?

Answer 13

You then have to change the final answer to be in the same number of decimal places

Question 14

When are zeros significant? Give an example

Answer 14

Any zeros shown on an ammeter for example that trail after a non-zero digit are significant

Question 15

What is the absolute uncertainty if you’re taking a single reading?

Answer 15

The resolution of the instrument

Question 16

Resolution of an instrument

Answer 16

The smallest digit

Question 17

When is the absolute uncertainty the resolution of the instrument?

Answer 17

If you’re taking a single reading

Question 18

When could you argue that the absolute uncertainty is double?

Answer 18

If it’s something that you have to line up with zero at the start (e.g: measuring the length of something with a ruler)

Question 19

What could you argue if you’re measuring something where you have to line it up with zero at the start (e. - measuring the length of something with a ruler)

Answer 19

Twice the absolute uncertainty

Question 20

What would you need to do if you are using double the absolute uncertainty since you’re measuring with something where you have to physically line the equipment up with zero? Give an example

Answer 20

Make it clear that this is exactly how you got the absolute uncertainty
e.g - absolute uncertainty with a ruler +-0.1cm, or +-0.2cm (+-0.1cm each end)

Question 21

What do we need to do to uncertainties if we have indices?

Answer 21

Multiply up

Question 22

What do we do in terms of uncertainties if a value is square rooted?

Answer 22

Halve the value