Practical skills

Question 1

When calculating an answer what is the appropriate number of significant figures to give your answer in?

Answer 1

The same as the value in the question with less number of significant figures.

Question 2

State the uncertainty when using vernier callipers

Answer 2

0.1 cm

Question 3

State the uncertainty when using a micrometer

Answer 3

0.1 mm

Question 4

Define repeatable

Answer 4

When the person carrying out the experiment obtains similar results

Question 5

Define reproducible

Answer 5

When another group carry out the experiment and obtain a similar pattern in their results

Question 6

Define resolution

Answer 6

The smallest change an instrument can detect or display

Question 7

Define accurate results

Answer 7

When the measured quantity has a value close to the true value

Question 8

Define precision

Answer 8

When repeat readings have a small spread in the data

Question 9

Define uncertainty

Answer 9

How accurately you can take a measurement or an expression of the spread of values taken.

Question 10

How can you find the uncertainty in a single measurement

Answer 10

Your estimate using the precision of the equipment as a guide

Question 11

How can the uncertainty be calcualted when you have repeat readings?

Answer 11

Range / 2

Question 12

When an equation has addition or subtraction can you add the uncertainty or percentage uncertainty?

Answer 12

uncertainty

Question 13

When an equation has multiplication or division can you add the uncertainty or percentage uncertainty?

Answer 13

percentage uncertainty

Question 14

Define percentage uncertainty stating its equation

Answer 14

It is the percentage error in your measurements.

Percentage uncertainty = uncertainty / mean value (x100%)

Question 15

Explain how you can find the percentage uncertainty in a gradient

Answer 15

1. Find the gradient of the best line of fit.
2. Draw a worst case LOBT and find its gradient.
3. Calculate the percentage difference between the two values.

Question 16

Explain how you can find the percentage uncertainty in an intercept

Answer 16

1. Find the intercept from the best line of fit.
2. Draw a worst case LOBT and find its intercept.
3. Calculate the percentage difference between the two values.

Question 17

Define a reading

Answer 17

The value is found from a single judgment when using a piece of equipment. e.g. thermometer, measuring cylinder. the uncertainty is given as half the precision

Question 18

Define a measurement

Answer 18

The value taken as the difference between the judgement between two values e.g. ruler.

The uncertainty is given as half the precision x by 2

Question 19

Define random error

Answer 19

Is an error that is different for every reading. This causes repeat readings to spread around the true value and scatter around the line of best fit

Question 20

Define systematic error

Answer 20

The same error on all readings. It will shift all results and gradient up or down.