1
Q
What are the seven SI base units?
A
- mass = kilogram (kg)
- length = metre (m)
- time = second (s)
- current = ampere (A)
- temperature = kelvin (K)
- amount of substance = mole (mol)
- luminous intensity = candela (cd)
2
Q
What is the Newton (N) equivalent to in base units?
A
- F = ma
- N = kg x ms-2 = kgms-2
- N = kgms-2
3
Q
What is the Joule (J) equivalent to in base units?
A
- Energy = 1/2 x mass x velocity2
- J = kg x (ms-1)2 = kg m2 s-2
- J = kg m2 s-2
4
Q
What is the Pascal (Pa) equivalent to in base units?
A
- Pressure = force/area
- Pa = N/m2 = (kgms-2)/m2 = kg m-1 s-2
- Pa = kg m-1 s-2
5
Q
What is meant by the resolution of a measuring instrument?
A
The smallest change in the division of its scale
6
Q
What’s the typical resolution of a metre ruler?
A
1mm
7
Q
What’s the typical resolution of a vernier calliper?
A
0.05mm
8
Q
What’s the typical resolution of a micrometer screw gauge?
A
0.001mm
9
Q
What’s the typical resolution of a top-pan balance?
A
0.01g
10
Q
What’s the typical resolution of a protractor?
A
1º
11
Q
What’s the typical resolution of a stopwatch?
A
0.01s
12
Q
What’s the typical resolution of a thermometer?
A
1ºC
13
Q
What’s the typical resolution of a voltmeter?
A
1mV - 0.1V
14
Q
What’s the typical resolution of an ammeter?
A
1mA - 0.1A
15
Q
What’s the typical resolution of an oscilloscope?
A
1Hz
16
Q
What’s the typical resolution of a laser?
A
450 - 650nm
17
Q
What is meant by an analogue scientific instrument?
A
An instrument that transfers information through electric pulses of varying amplitude (meaning they can’t be easily read by a computer)
18
Q
What are some features of anologue scientific instruments?
A
- They are cheaper
- Have lower accuracy and resolution
- More sensitive
- Usually involves a pointer which indicates a value based on its angle or position on the scale
19
Q
What is meant by a zero error?
A
When a measuring system gives a false reading when the true value of a measured quantity is zero
20
Q
What is meant by parallax error?
A
An error in a reading caused by not reading the measurement at eye level
21
Q
What types of error are anologue meters subject to?
A
- Zero error
- Parallax error
22
Q
What is meant by a digital scientific instrument?
A
A meter that translates information into binary (0 or 1) format (which can then be read and analysed by a computer)
23
Q
What are some features of a digital scientific instrument?
A
- They are more expensive
- Have a greater accuracy and resolution than analogue instruments
- Show measured values as digits
- Easy to use because they give a specific (and generally more precise) value
24
Q
What types of error are digital meters subject to?
A
- Zero error
25
How is **zero error** accounted for in an experiment?
The "zero" value must be subtracted from the end results
26
What is meant by an **auto-range function** on a digital meter?
It can show very low or very high values depending on the readings
27
How is the **auto-range function** on a digital meter useful?
It saves time selecting an instrument with the correct range and precision for each experiment
28
What is a micrometer (screw gauge)?
A tool used for measuring small widths, thicknesses or diameters (e.g. the diameter of a copper wire)
29
What are the two scales that make up a micrometer?
* The main scale / barrel (on the **sleeve**)
* The thimble scale (a rotating scale on the **thimble**)
30
What is the **resolution** of a micrometer?
0.01mm
31
How do you clamp the spindle and anvil around the object being measured on a **micrometer**?
By rotating the ratchet
32
Why should the spindle of a micrometer never be tightened using the **barrel**?
As it may increase the chances of overtightening and zero errors
33
Where is the value measured by a micrometer read?
Where the **thimble** scale aligns with the **main** scale
34
On a micrometer, what does each division of the **main scale** represent?
0.5mm
35
On a micrometer, what does each division of the **thimble scale** represent?
0.01mm
36
How is the measurement of an object taken from a micrometer?
1. Read the **main scale** first, which is the one on the sleeve/barrel (each division is usually 0.5mm)
2. The **amount of division lines** **multiplied** by 0.**5mm** gives the **main scale reading**
3. Read the **thimble scale**, which is the one on the rotating part (each division is 0.01mm)
4. **Find which line on the thimble** lines up exactly with the main horizontal line
5. **Multiply** the thimble number by 0.01mm to get the **thimble reading**
6. **Add** the **main scale reading** and the **thimble reading** together to get the **final value** to 2 decimal places
37
What is a vernier caliper?
A tool for measuring distance that uses a sliding vernier scale to measure diameters, thicknesses and the length of small objects (e.g. a screw or the depth of a hole)
38
What is the most common **resolution** of a vernier caliper?
0.1mm
(However, some are as small as 0.02mm - 0.05mm)
39
What are the two scales that make up a vernier caliper?
* The **main** scale
* The **vernier** scale
40
How is an object clamped in a vernier caliper?
The **two** **upper or lower jaws** are clamped around the object, the **sliding vernier scale** will follow this and can be held in place using the **locking screw**
41
What are the **lower jaws** of a vernier caliper used for?
Measuring the size of an object **inside** the jaws (**internal**)
42
What are the **upper jaws** of a vernier caliper used for?
Measuring the size of an object **either side** of the jaws (**external**)
43
What does each long line on the **main scale** of a vernier caliper represent?
1cm
44
What does each division on the **main scale** of a vernier caliper represent?
1mm
45
What does each division on the **vernier scale** of a vernier caliper represent?
0.1mm
46
1. Read the **main scale** and look for the last whole millimetre (mm) to the left of the zero on the vernier scale
2. Read the **vernier scale**, find the liner on the vernier scale that **exactly** lines up with any line on the main scale and note the value (usually tenths of a mm)
3. Add the two readings together to get your final measurement (recording the answer to at least 1 decimal place)
47
Why is a vernier caliper easier to use for many measurements than a micrometer?
* In general, the micrometer has a smaller measuring range than a vernier caliper
* Even though the micrometer has a better accuracy, the vernier caliper is quicker to use (since the micrometer involves rotating the thimble)
48
What is a signal generator?
An electronic test instrument used to create repeating or non-repeating waveforms (which can be adjusted for different shapes and amplitudes)
49
What are signal generators often used for?
* Creating signals to then show on **oscilloscopes**
* The designing and repairing of electronic devices to check they are working as expected
50
What is a Cathode-Ray Oscilloscope (CRO)?
A laboratory instrument used to display, measure and analyse waveforms of electrical circuits. Therefore it can be used as an a.c and d.c voltmeter.
51
What does a **transverse wave** on an **oscilloscope** suggest about the voltage?
It is an a.c voltage (alternating current)
52
What can a transverse wave from an a.c voltage on an oscilloscope be used to determine?
* Frequency of the wave
* Time period of the wave
* Peak voltage
53
What does a **horizontal line** on an **oscilloscope** suggest about the voltage?
It is a d.c voltage (direct current)
54
What does the **x-axis** of an oscilloscope show?
Time
55
What does the **y-axis** of an oscilloscope show?
Voltage (or y-gain)
56
What is meant by the **time-base** of an oscilloscope?
The amount of time that each division (square) represents
57
What is the **time-base** of an oscilloscope commonly measured in?
Seconds per division
(s div-1)
58
What are the controls of the **time base** of a cathode-ray oscilloscope for an **A.C** waveform?
* When the **time-base** is switched **off**, only a **vertical line** on the **voltage-gain axis** (y-axis) is seen with its relevant amplitude
* When the **time-base** is switched **on**, a wave will appear across the whole screen and the time period can be measured
* This control has units of **time div-1** and has a range of 100ms - 1μs per division
59
What are the controls of the **voltage-gain** (sensitivity) of a cathode-ray oscilloscope for an **A.C** waveform?
* This controls the vertical deflection (amplitude) of the wave
* The **peak voltage** (V0) is the maximum vertical displacement measured from the time axis
* The **peak-to-peak voltage** is the vertical displacement between the minimum and maximum values of voltage
* When the **voltage-gain** is switched **off**, only a horizontal line on the time axis will be seen
* This control has units of **volts div-1**
60
What are the controls of the **time base** of a cathode-ray oscilloscope for a **D.C** waveform?
* Only a horizontal line is displayed at the relevant voltage
* Therefore, the **time-base** settings are **irrelevant** since there is **no time period**
61
What are the controls of the **voltage-gain** of a cathode-ray oscilloscope for a **D.C** waveform?
* Only a horizontal line is displayed at the relevant voltage
* The **voltage-gain** setting **is** relevant since this is used to read the value of the d.c voltage
62
What are the **errors** in measuring time using a stopwatch?
* **Human reaction time** (on average about 0.25s) - Random error
* **Accidentally** pressing the start/stop button too many times - Random error
* Consistently starting the stopwatch **too late or too early** - Random error
* The **mechanism of the stopwatch** (older stopwatches may have a slight delay) - Systematic error
63
How can the errors from measuring time with a stopwatch be reduced?
By repeating readings and taking an average (mean)
64
What is a light gate?
A digital switch-type sensor which is used in time experiments for moving objects
65
How do light gates work?
* They consist of an infrared transmitter and receiver between the 'gate'
* When this signal is obstructed by an object, a timer can be started or stopped depending on its configuration
* If the distance between two light gates is known, then the time interval for an object to pass between both gates can be used to measure its speed (v = s/t)
66
What are data loggers?
A tool that allows for the quick and efficient gathering of data
67
What do data loggers do?
* They automatically monitor environmental parameters over time such as temperature, pressure, voltage or current using multiple sensors, and they record and store the data in a computer chip
* They allow for the information that they contain to be inputted into a computer and formatted into a table.
* After this is done, the computer is able to calculate the average and plot graphs using the data and calculate gradients, quicker and more accurately than humans.
68
What are the benefits of using data loggers?
* Readings are taken with **higher** degrees of **accuracy**
* Reduction of **human error** (e.g. reaction times, subjectiveness)
* Readings can be taken over a **long period of time** (e.g. hourly readings of temperature over many days)
* Readings can be taken in a **very short period of time**, where it would be too quick for the human eye to see a difference
* Reduction in safety risks with **extreme conditions** such as measuring the temperature of boiling water
69
What is computer modelling?
The processing of the data collected from a physics experiment into a **software** or a **spreadsheet** (commonly done in conjunction with data loggers)
70
What is the benefit of computer modelling?
Time can be sped up to predict the future outcome of an experiment
71
What are some examples of physical quantities that are useful for when making estimates?
* Diameter of an atom = 10-10m
* Wavelength of UV light = 10nm
* Height of an adult human = 2m
* Distance between the Earth and the Sun = 1.5 x 108m
* Mass of a hydrogen atom = 10-27kg
* Mass of an adult human = 70kg
* Mass of a car = 1000kg
* Seconds in a day = 90000s
* Seconds in a year = 3 x 107s
* Speed of sound in air = 300 ms-1
* Power of a lightbulb = 60W
* Atmospheric pressure = 1 x 105 Pa
72
What is meant by a **true value**?
A perfect measurement value which reflects the quantity being measured with no errors.
73
Why is it **impossible** to obtain the true value of any quantity?
There will always be a degree of **uncertainty** in reality, which can be seen when you repeat a measurement and get a different result
74
What is meant by **random error**?
A type of error that causes **unpredictable fluctuations** in an instrument's readings as a result of uncontrollable factors (e.g. environmental conditions).
This type of error affects the **precision** of the measurements taken, causing a wider spread of results about the mean value.
75
How can random errors be reduced?
By repeating measurements several times and calculating an average from them
76
What is meant by a **systematic error**?
A type of error that arises from the use of **faulty instruments** or from **flaws** in the **experimental method**.
This type of error is repeated consistently every time the instrument or method are used, which affects the **accuracy** of all readings obtained.
77
How can systematic errors be reduced?
* Instruments should be **recalibrated**, or different instruments should be used
* Corrections or adjustments should be made to the technique
78
What is meant by **precision**?
The **closeness** of consistency between values obtained by repeated measurements.
This is influenced only by random effects and can be expressed numerically by measures such as standard deviation.
A measurement is **precise** if the values 'cluster' closely together.
79
What is meant by **accuracy**?
How close a measurement is to the true value.
It is a quality denoting the **closeness** of consistency between **measured values** and **true value**
It **cannot** be quantified and is influenced by random and systematic errors.
80
What is meant by an **uncertainty**?
An estimate of the difference between a measurement reading and the true value.
It is the interval within which the true value can be considered to lie with a given level of **confidence** or **probability**.
Any measurement will have some uncertainty about the result, which will come from variations in the data obtained and be subject to systematic or random effects.
81
What is the difference between **uncertainties** and **errors**?
* **Errors** can be thought of as **issues** with equipment or methodology that causes a reading to be different from the true value
* **The uncertainty** is a range of values around a measurement within which the true value is expected to be within (it is an **estimate**)
82
What is meant by **absolute** uncertainty?
Where uncertainty is given as a fixed quantity
83
What is meant by **fractional** uncertainty?
Where uncertainty is given as a fraction of the measurement
84
What is meant by **percentage** uncertainty?
Where uncertainty is given as a percentage of the measurement
85
What is the equation to calculate a percentage uncertainty?
percentage uncertainty = (uncertainty/measured value) x 100
86
How do you find the uncertainty in a **reading**?
Half the smallest division
(± 1/2 x resolution)
87
How do you find the uncertainty in a **measurement**?
At least ±1 smallest division
88
How do you find the uncertainty in **repeated data**?
Half the range
(± 1/2 x (nlargest - nsmallest))
Where:
* nlargest = the largest value
* nsmallest = the smallest value
89
How do you find the uncertainty in **digital readings**?
± the last significant digit unless otherwise quoted
90
How are **uncertainties combined** in terms of **addition**?
**Add** the **absolute** uncertainties together
90
How are **uncertainties combined** in terms of **multiplication**?
**Add** the **percentage** or **fractional** uncertainties
91
What is the **independent** variable?
The variable within an experiment that is changed
92
How are **uncertainties combined** in terms of **raising to a power**?
**Multiply** the **percentage** uncertainty by the **power**
93
What is the **dependent** variable?
The variable within an experiment that is measured
94
What is the **control** variable?
The variable within an experiment that does not change
95
When presenting data in tables, what variable should be displayed in the **first column**?
The independent variable
96
When presenting data in tables, what variable should be displayed in the **second column**?
The dependent variable (if taking repeated readings, then more columns should be added, including an extra column for the mean value at the end)
97
When presenting data in tables, what variables should be displayed after the **dependent variable**?
Any columns for processing data (e.g. calculations)
98
What is are some good ways to evaluate an experimental design (**peer review**)?
* By **repeating** the experiment (using the instructions provided)
* By determining the **reproducibility** of the experiment (whethere or not similar results can be achieved)
99
What is meant by an **implication of science** and what are the **possible implications**?
A **consequence** of the **scientific knowledge**
These could be:
* **Commercial** - concerning money (e.g. the funding for a scientific experiment)
* **Legal** - concerning law (e.g. copyright protection for data collections)
* **Ethical** - concerning moral principles (e.g. using animals or humans)
* **Social** - concerning society (e.g. how the results affect all members of society - children, elderly, disabled etc.)
100
What is the power of ten for the prefix **femto** (f)?
10-15
101
If a distance is given as 5fm (**femtometres**), what is the value in **metre**?
5 x 10-15 m
102
What is the power of ten for the prefix **pico** (p)?
10-12
103
A capacitor has a capacitance of 5pF (**picofarads**). What is this in **Farads**?
5 x 10-12 F
104
What is the power of ten for the prefix **nano** (n)?
10-9
105
Red light has a wavelength of 700nm (**nanometres**). What is the wavelength value in **metres**?
700 x 10-9 m
**OR**
7 x 10-7 m
106
What is the power of ten for the prefix **micro** (μ)?
10-6
107
A current is 50 μA (**microamperes**). What is this in **Amperes**?
50 x 10-6
**OR**
5 x 10-5
108
What is the power of ten for the prefix **milli** (m)?
10-3
109
A wire has a diameter of 2mm (**millimetres**). What is this in **metres**?
2 x 10-3 m
110
What is the power of ten for the prefix **centi** (c)?
10-2
111
An object moves 15cm (**centimetres**). What is this in **metres**?
15 x 10-2 m
**OR**
1.5 x 10-1 m
**OR**
0.15 m
112
What is the power of ten for the prefix **kilo** (k)?
103
113
A car travels at 20 km s-1 (**kilometres per second**). What is its speed in **metres per second**?
20 x 103 ms-1
**OR**
2 x 104 ms-1
114
What is the power of ten for the prefix **mega** (M)?
106
115
A power station outputs 500MW (**megawatts**). What is this power in **Watts**?
500 x 106 W
**OR**
5 x 108 W
116
What is the power of ten for the prefix **giga** (G)?
109
117
A photon has a frequency of 4 GHz (**gigahertz**). What is the frequency in **Hertz**?
4 x 109 Hz
118
What is the power of ten for the prefix **tera** (T)?
1012
119
A hard drive stores 2TB (**terabytes**). What is this value in **Bytes**?
2 x 1012 B
120
What is the power of ten for the prefix **peta** (P)?
1015
121
A laser pulse has an energy of 10 PJ (**petajoules**). What is this value in **Joules**?
10 x 1015
**OR**
1 x 1016
122
What is 1mm2 (millimetres squared) in **m2** (**metres squared**)?
1 x 10-6 m2
Because:
* (10-3 m)2 = 10-6 m2
123
What is 1cm3 (centimetres cubed) in **m3** (**metres cubed**)?
1 x 10-6 m3
Because:
* (10-2 m)3 = 10-6 m3
A-Level Physics Edexcel
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