Practical Handbook Notes

Question 1

How should quantities and their units be written in a table?

Answer 1

With the symbol for the quantity, a slash and its respective unit. eg L/m

Question 2

Which columns (right or left) should the independent and dependent variables be in for a table?

Answer 2

Independent in the left hand column, dependent in the right hand column

Question 3

Should the body of a table include units?

Answer 3

No

Question 4

Do tabulated logarithmic values have units?

Answer 4

No

Question 5

How can we show that logarithmic values are of a certain quantity and their respective unit?

Answer 5

log (time/s)

Question 6

For data written in tables, how should the number of significant figures be determined? Give an example.

Answer 6

It should be determined by the resolution of the device used to measure it or the uncertainty in the measurement eg 60cm measured on a regular metre rule should be written as 600mm, 60.0cm or 0.600m

Question 7

If the number of decimal places is changed as data crosses a multiple of ten (eg 99.7, 99.9, 100.1), should you alter the number of significant figures or the number of decimal place?

Answer 7

The significant figures as changing the number of decimal places alters the accuracy of the data

Question 8

How many significant figures should calculated values be written too?

Answer 8

To the smallest number of significant figures in the table of measured data

Question 9

For equipment that measures to half a unit (eg a thermometer measuring to 0.5ºC), how many decimal place should data be written to?

Answer 9

One decimal place

Question 10

What would be the uncertainty in a measurement that is measured to half a unit (eg. 1.0ºC)?

Answer 10

+/- 0.25 however, this would be rounded to the same number of decimal places as the data, eg. 1.0 +/- 0.3ºC

Question 11

What are five areas that should be considered when assessing uncertainty?

Answer 11

• Resolution of instruments used
• Manufacturer’s tolerance on instruments
• Judgements (one or two)
• Procedures used (eg repeated readings)
• Increments used

Question 12

What element of uncertainty can we assess from an instrument’s resolution?

Answer 12

The minimum possible uncertainty

Question 13

When considering uncertainties, what would we consider ‘readings’?

Answer 13

Values found from a single judgment when using a piece of equipment

Question 14

When considering uncertainties, what would we consider ‘measurements’?

Answer 14

Values taken as the difference between the judgements of two values

Question 15

Give 5 examples of instruments that requires a ‘reading’.

Answer 15

• Thermometer
• Top ban balance
• Measuring cylinder
• Digital voltmeter
• Geiger counter

Question 16

Give 5 examples of instruments that requires a ‘measurement’.

Answer 16

• Ruler/protractor
• Vernier calliper
• Micrometer
• Stopwatch
• Analogue meter

Question 17

What is the uncertainty in a ‘reading’?

Answer 17

Plus or minus half of the smallest division

Question 18

Should uncertainties be written to the same number of significant figures as the value or greater?

Answer 18

The same eg. 2.40 +/- 0.01V

Question 19

What is meant by ‘initial value uncertainty’?

Answer 19

The uncertainty given by the instrument used

Question 20

Does initial value uncertainty always apply or can it be affected by a zero error? Are any instruments exempt from this, if so, state them and why?

Answer 20

It always applies and cannot be affected by a zero error, other than equipment such as balances or thermometers where the zero is set at the point of manufacture

Question 21

When using a given value, what should you assume the uncertainty to be?

Answer 21

+/-1 in the last significant digit, eg. 1.60 x 10^-19 +/-0.01 x 10^-19 C

Question 22

When measuring a number of instances to reduce the uncertainty (eg. measuring the thickness of several sheets of aluminium) how should you alter the uncertainty?

Answer 22

Take the uncertainty of the whole measurement and divide it by the number of sheets

Question 23

When measurements are repeated, how can the uncertainty be calculated?

Answer 23

By finding half the range of the measured values, eg.

Data: 1.23, 1.32, 1.27, 1.22

1.32-1.22 = 0.1

Uncertainty = 0.1 / 2 = +/-0.05

Question 24

How can percentage uncertainty be calculated?

Answer 24

percentage uncertainty = absolute uncertainty / value x 100

Question 25

What process (excluding calc) should be done to find the percentage uncertainty of a gradient?

Answer 25

Two lines should be drawn on the graph, one should be the ‘best’ line of best fit and the other should be the steepest or shallowest line of best fit possible from the data (error bars). Find the gradients of both lines

Question 26

What is the calculation for the percentage uncertainty in the gradient?

Answer 26

percentage uncertainty = (best-worst gradient) / best gradient x 100

Question 27

How should you draw error bars?

Answer 27

• Plot the data point at the mean value
• Calculate the range of the point, excluding anomalies
• Add error bars with lengths equal to half the range on either side of the data point

Question 28

How should you find the total uncertainty when adding quantities?

Answer 28

Add the absolute uncertainties

Question 29

How should you find the total uncertainty when multiplying or dividing quantities?

Answer 29

Add the percentage uncertainties

Question 30

How should you find the total uncertainty when raising a quantity to a power?

Answer 30

Multiply the percentage uncertainty by the power

Question 31

How should axis be labelled?

Answer 31

With the quantity being measured and its units, separated with a forward slash

Question 32

What 6 things should you consider when creating a scale for a graph?

Answer 32

• Maximum and minimum values for each variable
• Size of paper
• Whether 0.0 should be included as a data point
• If you need to find the y-intercept
• Drawing axis without difficult scale markings
• The graph should cover minimum of half the grid

Question 33

What three things should be considered when drawing a line of best fit?

Answer 33

• If it should be curved or straight
• Are there anomalous results
• Are there uncertainties in measurements

Question 34

What sort of error would cause a line of best fit that is anticipated to go through the origin to fail to do so?

Answer 34

A systematic error

Question 35

At what stage should anomalous points be ignored?

Answer 35

At the data analysis stage. They should be included when recording and plotting data

Question 36

What does each letter represent in the equation y=mx + c?

Answer 36

y - dependent variable
m - gradient
x - independent variable
c - y-intercept

Question 37

How can graphs be used to find the relationship between x and y?

Answer 37

Plot a range of graphs (eg. x against y, x against y^2, x against √y etc) and the closest to a straight line is a good candidate for the relationship between x and y

Question 38

How can graphs be used to find more complex relationships between variables?

Answer 38

Rearrange the equation into a form of y = mx + c