1 Measurements and their errors

Question 1

What are the fundamental (base) units

Answer 1

• Metre (m)
• kilogram (kg)
• second (s)
• Kelvin (K)
• mole (n)
• Ampere (A)

Question 2

What quantities are the fundamental (base) units for

Answer 2

• Length
• Mass
• Time
• Temperature
• Amount of substance
• Electrical current

Question 3

What are SI derived units?

Answer 3

Units that consist of the fundamental (base) units

For example: Newtons= kg m s^-2

Question 4

What are the SI prefixes
* kilo (k)
* Mega (M)
* Giga (G)
* Tera (T)
in standard form?

Answer 4

• 10³
• 10⁶
• 10⁹
• 10¹²

Question 5

What are the SI prefixes
* centi (c)
* milli (m)
* micro (μ)
* nano (n)
* pico (p)
* femto (f)
in standard form?

Answer 5

• 10^-2
• 10^-3
• 10^-6
• 10^-9
• 10^-12
• 10^-15

Question 6

What is 1 eV in J?

Answer 6

1.6*10^-19 J

Question 7

What is 1 J in eV?

Answer 7

6.25*10¹⁸ eV

Question 8

What is 1 kW h in J?

Answer 8

3.6*10⁶ J

Question 9

What is 1 J in kW h?

Answer 9

2.78*10^-7 kW h

Question 10

Define random error.

Answer 10

An error introduced by variables which you cannot control.

Question 11

Define systematic error.

Answer 11

An error introduced by the experimental apparatus or method.

Question 12

Define precision.

Answer 12

Repeated measurements that are bery similar to the calculated mean value.

Question 13

Define repeatability.

Answer 13

If the experiment can be repeated multiple times and get the same result.

Question 14

Define reproducibility.

Answer 14

If someone else can recreate the experiment using different equipment or methods and get the same result.

Question 15

Define resolution.

Answer 15

The smallest change that can be measured using the equipment that gives a readable change in the reading.

Question 16

Define accuracy.

Answer 16

How close a measurement or answer is to the true value.

Question 17

Define uncertainty.

Answer 17

The range within which you would expect the true value to lie.

Question 18

Define absolute uncertainty.

Answer 18

Is the uncertainty of a measurement given as a fixed quantity.

Question 19

Define fractional uncertainty.

Answer 19

Is the uncertainty given as a fraction of the measurement taken.

Question 20

Define percentage uncertainty

Answer 20

Is the uncertainty given as a percentage of the measurement.

Question 21

How would you represent uncertainty in the final answer for a quantity?

Answer 21

(Result ± uncertainty) units

Question 22

How would you combine absolute uncertainties?

Answer 22

When you add or subtract quantities, you add the absolute uncertainties for each value

Question 23

How would you combine percentage uncertainties?

Answer 23

When you multiply or divide quantities, you add the percentage uncertainties for each value

When a measurement is raised by a power n, the percentage uncertainty is multiplied by n.

Question 24

How would you represent uncertainty in a data point in a graph?

Answer 24

With error bars.

Question 25

How would you determine the uncertainty in the gradient of a striaght-line graph?

Answer 25

• Draw lines of best fit which have the maximum and minimum possible gradients for the data.
• Uncertainty is the difference between the best and worst gradients.

Both should go through all of the error bars.

Question 26

How would you determine the uncertainty in the intercept of a striaght-line graph?

Answer 26

• Draw lines of best fit which have the maximum and minimum possible intercepts for the data.
• Uncertainty is the difference between the best and worst intercepts.

Both should go through all of the error bars.

Question 27

What is an order of magnitude?

Answer 27

Powers of ten which describe the size of an object, and which can also be used to compare the sizes of objects.