1. Working as a Physicist

Question 1

What is precision?

Answer 1

Where the spread of data is small
So it doesn’t need to be accurate, but all results have to be close together

Question 2

What is accuracy?

Answer 2

then the result is close to the real value

Question 3

What is an error?

Answer 3

The difference between the measured result and the true value

Question 4

What is a controlled variable?

Answer 4

The variable that is unchanged and constant
E.g amount of seeds placed for plants to grow
for an equal test

Question 5

What is an independant variable?

Answer 5

A variable that you manipulate and isn’t influenced by other variables
E.g amount of water for a plant

Question 6

What’s a dependant variable?

Answer 6

A variable that changes due to a change of another variable
E.g size of the plant

Question 7

What are systematic errors?

Answer 7

Affect the accuracy due to the apparatus or faults
- causes results to be too high/ low by same amount

Question 8

How can we reduce systematic errors?

Answer 8

Calibrate apparatus
- identify how far off a scale is
Read the meniscus at eye level, to reduce parallax error

Question 9

What is zero error?

Answer 9

Zero error is a systematic error where a measuring instrument does not read zero when it should.

E.g A micrometer that reads +0.01 mm when fully closed → all measurements will be +0.01 mm too high unless corrected.

Question 10

What is a gross timing error?

Answer 10

A significant mistake in starting or stopping the timer at the wrong moment, leading to an anomalous (does not fit the pattern) reading

Question 11

What is a meniscus?

Answer 11

The curve at the top of a liquid, the centre of it where it’s straight is the meniscus

Question 12

What is parallax error?

Answer 12

Reading not at eye level makes a parallax error

Question 13

What is a random error?

Answer 13

​Unpredictable variation between measurements that leads to a spread of values about the true value
So they effect precision

Question 14

How do we reduce random errors?

Answer 14

Take at least 3 readings
use computers/ data loggers/ cameras
use appropriate equipment
- with high resolutions, like a micrometer

Question 15

What should be used to measure very small distances, like 1mm?

Answer 15

Vernier or digital Callipers

Vernier callipers = 0.1mm resolution
Digital calipers = 0.01mm resolution

Question 16

Why do we calculate a mean?

Answer 16

Reduce effect of random errors

Question 17

How do we find a percentage uncertainty from a table of values?

Answer 17

Find range/2
then (range/2)/mean x 100

range/2 as its each way.

Question 18

What is a resolution?

Answer 18

The resolution is how precise a price of equipment is
The higher the resolution, the lower the gaps of the instrument
A micrometer has a resolution of 0.1mm
A ruler has 1mm

Question 19

What does a high resolution result in and what doesn’t it guarantee?

Answer 19

Results in low uncertainty

But doesn’t guarantee accuracy or precision

Question 20

What’s an uncertainty?

Answer 20

The interval/ range in which the true value can be considered to lie

Question 21

Why may a measurement have an uncertainty? (3 reasons)

Answer 21

• Instrument is being used to make the measurement
• Way in which the measurement is made
• Quantity measured not being constant

Question 22

What are the 2 types of uncertainties?

Answer 22

Absolute uncertainty
Percentage uncertainty

Question 23

What is an absolute uncertainty?

Answer 23

An uncertainty given by a fixed quantity
E.g 7±0.6V

Question 24

What is the uncertainty of a measurement?

Answer 24

The uncertainty is half the resolution
E.g resolution=0.1mm
uncertainty=0.05mm

Question 25

How do we find the % uncertainty

Answer 25

(Uncertainty/measurement) x100 E.g ±0.05mm/1.10mm = ±4.5%

Question 26

How do we combine uncertainties to adding/ subtract? E.g R(1)+R(2)+R(3)

Answer 26

We add their absolute uncertainties E.g 0.05+0.05+0.05=±0.15V

Question 27

How do we combine uncertainties to multiply/divide? E.g R=V/I

Answer 27

We add their percentage uncertainties E.g 0.45%+4.2%=±4.65%

Question 28

How do we combine uncertainties with powers? E.g area=πr^2

Answer 28

We times the uncertainty by the power E.g 0.3%x2=0.6%

Question 29

How should we measure several small lengths, like the thickness of a washer?

Answer 29

Stack them together Increases the distance being measured Reducing %U

Question 30

What differences in results happen with using a stopwatch vs a data logger?

Answer 30

A stopwatch has reaction time So uncertainty in measurement of time is larger with the stopwatch than the data logger However timing multiple swings with a stopwatch reduces %U Also light gates are difficult to use with certain experiments, like a pendulum

Question 31

What are prefixes?

Answer 31

prefixes are the multiples before the units E.g x10^6

Question 32

What are all the prefixes?

Answer 32

Tera, T = x10^12 Giga, G = x10^9 Mega, M =x10^6 Kilo, k =x10^3 deci, d =x10^-1 centi, c =x10^-2 milli, m =x10^-3 micro, µ =x10^-6 nano, n =x10^-9 pico, p =x10^-12 femto, f =x10^-15 atto, a =x10^-18

Question 33

What is homogeneity?

Answer 33

An equation is homogeneous if both sides have identical SI base units If an equation is not homogeneous, it's invalid 'homo' - same 'genius' - kind E,g mgh=1/2mv^2 kgm^2s^-2=kgm^2s^-2

Question 34

What are SI base units?

Answer 34

System International (SI) units are used globally They are the fundamental quantities of things in the universe Everything else is derived from the base units - so derived units

Question 35

What are the 6 SI base units?

Answer 35

mass, m (kg) length, L (m) Time, t (s) Electric current, I (A) Thermodynamic temperature, T (k) Amount of substance, n (mol) Remember 'smAkmolkg' to remember the 6 needed

Question 36

How do you derive a unit into base units?

Answer 36

We need to find other formulas that have other units in them E.g Energy Energy=Fd, F=ma Energy=kgms^-2 x m Energy=kgm^2s^-2

Question 37

If a student takes a measurement, and the reading vary, Eg 3.2s, 3.2s, 3.3s What must you take from this?

Answer 37

That the uncertainty is 0.1s You shouldn't record the average

Question 38

What is a sampling rate?

Answer 38

The number of samples taken per second when converting a continuous signal (like sound) into a digital format. It is measured in Hertz (Hz).

Question 39

What does concentric mean?

Answer 39

Means having a common centre Often used to describe shapes, such as circles or rings, that share the same central point but have different sizes.

Question 40

Why is a data logger a good way of collecting data?

Answer 40

Data has been collected over long period of time, ornery good for a very short time Very useful when a number of quantities are being measured simultaneously Time interval is very short High sample rate Low uncertainty in measurement

Question 41

Why do you double the uncertainty when measuring a distance between two points?

Answer 41

You double the uncertainty because each end of the measurement has its own uncertainty. So, total uncertainty = uncertainty at one end + uncertainty at the other end E.g. If a ruler has ±0.05 cm uncertainty: Measuring from point A to point B means both A and B contribute uncertainty. So total uncertainty = 0.05 + 0.05 = 0.1 cm

Question 42

What goes on each axis in a graph of "log v against log b"?

Answer 42

y-axis: log v x-axis: log b Yes, this is the correct way mate

Question 43

How can you tell if a graph is an exponential decay curve?

Answer 43

- Would be in the form of Q=Q(0)e^-kt - Plot LnQ vs t - If straight line with negative gradient its exponential

Question 44

What can be criticised from a students table?

Answer 44

N of decimal places/ sf Positions of where ended up not recorded etc / not just extension etc

Question 45

What are the benefits of using an oscilloscope over a voltmeter for an AC Voltage?

Answer 45

Voltmeter must measure alt p.d - or would read 0 AC voltmeter would give rms p.d directly Voltmeter may draw current and affect circuit its connected to

Question 46

What are advantages of using a reference load?

Answer 46

Changes in recorded length are minimised due to the support not bending Allows use of a vernier scale to determine the extension A load is placed on it to keep the wire taut/straight/under tension

Question 47

How can the extension of string be determined as accurately as possible? (When coming off table)

Answer 47

Read metre rule at eye level to avoid parallax Bring metre rule closer to avoid parallax Use set square to read position of bottom of mass holder Use plumb line to check that metre rule is vertical Record positions of mass holder when loading and unloading and calc mean

Question 48

What is a set square?

Answer 48

A triangular tool used to ensure objects or lines are aligned at a right angle (90°), typically to a ruler, bench surface, or another line — helping to reduce parallax errors and improve accuracy.

Question 49

What is a plumb line?

Answer 49

A piece of string with a weight at the bottom, used to find a true vertical line To ensure something is perfectly vertical

Question 50

What precaution should a student use when measuring lighting?

Answer 50

Carry out experiment under subdued lighting As ambient lighting will increase ammeter reading Meaning less background lighting effecting results

Question 51

What's subdued lighting?

Answer 51

Subdued lighting means the light in the room is dimmed or reduced, often used to make certain features (like light beams or interference patterns) easier to observe in practical experiments.

Question 52

What's ambient lighting?

Answer 52

Ambient lighting is the general background light present in a room or environment — it’s the overall level of illumination not directed or focused on anything specific.