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A-Level Course Notes: PHYSICS
SECTION I: General Physics
SECTION I
General Physics
CIE A-Level [AS and A2]
________________________
Course Notes
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A-Level Course Notes: PHYSICS
SECTION I: General Physics
Syllabus Details______________________
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A-Level Course Notes: PHYSICS
SECTION I: General Physics
1. Physical Quantities and Units_______________
Content
1.1 Physical quantities [AS]
1.2 SI Units [AS]
1.3 The Avogadro constant [A2]
1.4 Scalars and vectors [AS]
Learning outcomes_____________________________________
Candidates should be able to:
(a) show an understanding that all physical quantities consist of a numerical
magnitude and a unit
Physical Quantity
25 ms-2
Unit
Numerical magnitude
From the syllabus...
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A-Level Course Notes: PHYSICS
SECTION I: General Physics
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A-Level Course Notes: PHYSICS
SECTION I: General Physics
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A-Level Course Notes: PHYSICS
SECTION I: General Physics
(b) recall the following SI base quantities and their units: mass (kg), length (m), time
(s), current (A), temperature (K), amount of substance (mol)
Base Quantity
length
mass
time
electric current
temperature
amount of substance
Unit
meter
kilogram
second
ampere
kelvin
mole
Symbol
m
kg
s
A
K
mol
(c) express derived units as products or quotients of the SI base units and use the
named units listed in this syllabus as appropriate
Example of derived units
Quantity
SI Derived Unit Symbol Unit
SI Base Unit
frequency
hertz
Hz
-
s-1
force
newton
N
-
m·kg·s-2
pressure, stress
pascal
Pa
N/m2
m-1·kg·s-2
energy, work, quantity of heat
joule
J
N·m
m2·kg·s-2
power, radiant flux
watt
W
J/s
m2·kg·s-3
electric charge, quantity of electricity
coulomb
C
-
electric potential difference,
electromotive force
volt
V
W/A
m2·kg·s-3·A-1
capacitance
farad
F
C/V
m-2·kg-1·s4·A2
electric resistance
ohm
V/A
m2·kg·s-3·A-2
electric conductance
siemens
S
A/V
m-2·kg-1·s3·A2
magnetic flux
weber
Wb
V·s
m2·kg·s-2·A-1
kg·s-2·A-1
m2·kg·s-2·A-2
s·A
magnetic flux density
tesla
T
Wb/m2
inductance
henry
H
Wb/A
Celsius temperature
degree Celsius °C
-
K
(c)
luminous flux
lumen
lm
cd·sr
illuminance
lux
lx
lm/m2
activity (of a radionuclide)
becquerel
Bq
-
m2·m-2·cd = cd
m2·m-4·cd = m-2·cd
s-1
(d) use SI base units to check the homogeneity of physical equations
Each side of an equation must have the same base units
F
=
[N]
=
-2
[mkgs ] =
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m
[kg]
[kg]
x
a
[ms-2]
[ms-2]
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A-Level Course Notes: PHYSICS
SECTION I: General Physics
(e) show an understanding of and use the conventions for labelling graph axes and
table columns as set out in the ASE publication Signs, Symbols and Systematics (The
ASE Companion to 16–19 Science, 2000)
CONVENTIONS FOR TABLES (From the syllabus)
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A-Level Course Notes: PHYSICS
SECTION I: General Physics
CONVENTIONS FOR GRAPHS (From the syllabus)
Dependent variable / units
Plotting graphs
Best fit line
Steepest Gradient
Maximum
intercept
Shallowest Gradient
Error Bars
Minimum
intercept
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Independent variable / units
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A-Level Course Notes: PHYSICS
SECTION I: General Physics
(f) use the following prefixes and their symbols to indicate decimal submultiples or
multiples of both base and derived units: pico (p), nano (n), micro (μ), milli (m),
centi (c), deci (d), kilo (k), mega (M), giga (G), tera (T)
(g) make reasonable estimates of physical quantities included within the syllabus
Remember: an estimate does not have to be exactly correct and often just expresses an
order of magnitude.
e.g. The mass of universe is ~1050 kilograms
(h) show an understanding that the Avogadro constant is the number of atoms in
0.012 kg of carbon-12
The Avogadro number:
The number of atoms in 0.012kg of carbon-12.
It is 6.02x1023
(i)
use molar quantities where one mole of any substance is the amount
containing a number of particles equal to the Avogadro constant
Mole:
One mole of a substance is the amount of that substance that
contains the same number of atoms as 0.012kg of carbon-12.
Molar Mass: The mass of one mole of a substance is called the molar mass.
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A-Level Course Notes: PHYSICS
SECTION I: General Physics
(j) distinguish between scalar and vector quantities and give examples of each
Vector:
Scalar:
Quantity with both magnitude and direction
Quantity with only magnitude
Vectors
Scalars
Displacement
Distance
Velocity
Speed
Acceleration
Mass
Force
Energy
Momentum
Temperature
Electric Field Strength
Potential Difference
Magnetic Field Strength
Density
Gravitational Field Strength
Area
(k) add and subtract coplanar vectors
Vector addition and subtraction
4N
7N
=
3N
4N
=
5N
3N
4N
=
1N
3N
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A-Level Course Notes: PHYSICS
SECTION I: General Physics
(l) represent a vector as two perpendicular components.
x sin 
Vector components
x

x cos 
SEE PHET SIM
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A-Level Course Notes: PHYSICS
SECTION I: General Physics
2. Measurement Techniques___________________
Content
2.1 Measurements
2.2 Errors and uncertainties
Learning outcomes_____________________________________
Candidates should be able to:
(a) use techniques for the measurement of length, volume, angle, mass, time,
temperature and electrical quantities appropriate to the ranges of magnitude
implied by the relevant parts of the syllabus.
In particular, candidates should be able to:
• measure lengths using a ruler, vernier scale and micrometer
Micrometer
Vernier
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A-Level Course Notes: PHYSICS
SECTION I: General Physics

When using a ruler, be careful of parallax errors
• measure weight and hence mass using spring and lever balances
• measure an angle using a protractor
• measure time intervals using clocks, stopwatches and the calibrated timebase of a cathode-ray oscilloscope (c.r.o.)
• measure temperature using a thermometer as a sensor
• use ammeters and voltmeters with appropriate scales
• use a galvanometer in null methods
Voltage measurements
Galvanometer
multiplier
Galvanometer
Current measurements
Shunt
A Galvanometer is a current measuring meter that can be used in two ways…


With a resistor in series to measure voltage
With a resistor in parallel to measure current
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A-Level Course Notes: PHYSICS
SECTION I: General Physics
• use a cathode-ray oscilloscope (c.r.o.)
KEY CONTROLS….


Time base: Time taken for beam to pass through one horizontal division [Sec/div]
Vertical amplifier gain: The vertical scale control [Volts/div]
• use a calibrated Hall probe
Basic Structure of a Hall probe…



A small piece of semi-conductor material placed perpendicular to the
magnetic field
A current is paced through the semi-conductor
A voltage (Hall voltage) is measured which is proportional to the magnetic
flux density
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A-Level Course Notes: PHYSICS
SECTION I: General Physics
(b) use both analogue scales and digital displays
Analogue and Digital Displays
Digital Scale
Analogue Scale
Error is half the smallest division
+/- 2.5
Error is the last decimal place
+/- 0.01
(c) use calibration curves
Real value
Calibration curve
Measured value


Record value from instrument
Use calibration curve to read off the corrected “real” value
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A-Level Course Notes: PHYSICS
SECTION I: General Physics

(d) show an understanding of the distinction between systematic errors
(including zero errors) and random errors
Random Errors
Systematic Errors
Changes conditions or surroundings of
equipment
Zero error on instrumentation
Non-perfect observations by
experimentalist
Wrong calibration of instrumentation
Readability of equipment
Incorrect measurement method for every
measurement
Random Errors:
Errors that can not be predicted.
Systematic Errors: Errors which are the same for each measurement
(e) show an understanding of the distinction between precision and accuracy
Small random error
Small systematic error
# of measurements
Imprecise and accurate
Precise and accurate
# of measurements
Precision:
Accurate:
reading
reading
value
Imprecise and inaccurate
# of measurements
# of measurements
value
Precise and inaccurate
reading
reading
value
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A-Level Course Notes: PHYSICS
SECTION I: General Physics
(f) assess the uncertainty in a derived quantity by simple addition of actual,
fractional or percentage uncertainties (a rigorous statistical treatment is not
required).
Absolute uncertainty:
Fractional uncertainty:
Percentage uncertainty:
Size of an error and its units
Absolute uncertainty / measurement
Fractional uncertainty x 100%
Addition and Subtraction
5.9 ±0.6m + 3.9 ±0.8m = 9.8 ±1.4m (add absolute errors)
6.9 ±0.6m - 3.9 ±0.8m = 3.0 ±1.4m (add absolute errors)
Multiplication and Division
5.6 ±0.5m x 2.6 ±0.5m = 15 ±??m
0.5 / 5.6 = 0.089
0.5 / 2.6 = 0.19
Sum of relative errors = 0.28
Absolute error = 0.28 x 15 = 4.2m
FINAL ANSWER = 15 ±4 m
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A-Level Course Notes: PHYSICS
SECTION I: General Physics
Background Reading_________________
PHYSICS, Giancoli 6th edition, Chapter 1
Useful Websites______________________
http://phet.colorado.edu/en/simulations/category/new
http://www.s-cool.co.uk/alevel/physics.html
http://www.physicsclassroom.com/mmedia/index.cfm
http://www.phys.hawaii.edu/~teb/java/ntnujava/index.html
http://www.colorado.edu/physics/2000/index.pl
Constants___________________________
[These are given on each test paper]
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