Working as a physicist

Question 1

Femto

Answer 1

x10 ^-15

Question 2

Pico

Answer 2

x10 ^-12

Question 3

Nano

Answer 3

x10 ^-9

Question 4

Micro

Answer 4

x10 ^-6

Question 5

Milli

Answer 5

x10 ^-3

Question 6

Kilo

Answer 6

x10 ^3

Question 7

Mega

Answer 7

x10 ^6

Question 8

Giga

Answer 8

x10 ^9

Question 9

Tera

Answer 9

x10 ^12

Question 10

What is uncertainty?

Answer 10

The interval in which the true value lies/the range of possible values

Question 11

What is the error in a result?

Answer 11

The difference between the measured value and the true value

Question 12

What is % uncertainty?

Answer 12

The uncertainty calculated as a percentage of the measured value

Question 13

What is resolution?

Answer 13

The smallest measuring interval in a single reading. Resolution can give the uncertainty, but for instruments such as a stopwatch, human reaction time also contributes to uncertainty, so resolution cannot give uncertainty

Question 14

What is the range?

Answer 14

The largest value minus the smallest value (in repeated readings)

Question 15

What is precision?

Answer 15

Indicates the consistency between repeated values

Question 16

Why is it better to measure larger values?

Answer 16

A larger value will give a much smaller percentage uncertainty, assuming the uncertainty is fixed

Question 17

How should you estimate the uncertainty for a single measurement?

Answer 17

Given by half the smallest increment on the device. However, for instruments such as a ruler, the increment is the uncertainty, as 2 measurements are made.

Question 18

How should you estimate the uncertainty for repeated readings?

Answer 18

Uncertainty is half the range, and % uncertainty is half range divided by mean

Question 19

For calculated values, how should you combine uncertainties?

Answer 19

Add the % uncertainties (generally while multiplying or dividing results)

Question 20

What is the purpose of error bars?

Answer 20

To visually represent the uncertainty, to allow a line of worst fit to be drawn which then allows for an uncertainty in the gradient to be calculated - difference between line of best fit and line of worst fit

Question 21

What are the key steps of the scientific process?

Answer 21

• Creation and testing of theories
• Peer review
• Publication of results in scientific journals
• Testing of results by other scientists
• Acceptation of theory if supported by enough evidence

Question 22

What are the 7 base quantities and their units?

Answer 22

• Mass (kg, kilogram)
• Length (m, metre)
• Time (s, seconds)
• Current (A, ampere)
• Temperature (K, kelvin)
• Amount of substance (mol, mole)
• Luminous intensity (cd, candela)

Question 23

What are the most important things to consider when designing/evaluating an experiment?

Answer 23

• Does the method test what it set out to?
• Is the method clear enough?
• Are control variables properly controlled?
• Has appropriate apparatus been selected and will it be used correctly?
• Will enough repeated measurements be taken?
• Is the experiment safe?
• Are there any other ethical considerations?

Question 24

How should you combine uncertainties when adding or subtracting data?

Answer 24

Add absolute uncertainties

Question 25

How should you combine uncertainties when multiplying or dividing data?

Answer 25

Add the percentage uncertainties

Question 26

How should you combine uncertainties when raising to a power?

Answer 26

Multiply percentage uncertainty by the power

Question 27

What are systematic errors?

Answer 27

Errors that are the same every time an experiment is carried out, often caused by issues with the apparatus or the way the experiment is carried out. This includes zero errors.
Systematic errors affect the accuracy of the results, but not the precision, and can be identified when results are compared to another person’s, but are hard to see when considered in isolation.
To avoid them, check apparatus before and experiment begins

Question 28

What are random errors?

Answer 28

Random errors vary and they are the cause of results being slightly different each time an experiment is repeated.
They are easier to spot than systematic errors and they affect the precision of results.
Using apparatus with better resolution can reduce the size of random errors in individual measurements, and doing more repeats then calculating an average also helps eliminate random error.