A-Level Course Notes: PHYSICS

SECTION I: General Physics

SECTION I

General Physics

CIE A-Level [AS and A2]

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Course Notes
Syllabus Details______

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

From the syllabus...

(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 / Unit / Symbol
length / meter / m
mass / kilogram / kg
time / second / s
electric current / ampere / A
temperature / kelvin / K
amount of substance / mole / 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

(d) use SI base units to check the homogeneity of physical equations

Each side of an equation must have the same base units

F = m x a

[N] = [kg] [ms-2]

[mkgs-2] = [kg] [ms-2]

(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)

CONVENTIONS FOR GRAPHS (From the syllabus)

(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.

(j) distinguish between scalar and vector quantities and give examples of each

Vector: Quantity with both magnitude and direction

Scalar: Quantity with only magnitude

(k) add and subtract coplanar vectors

(l) represent a vector as two perpendicular components.

SEE PHET SIM

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

· 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 time-base 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

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

• 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

(b) use both analogue scales and digital displays

· Record value from instrument

· Use calibration curve to read off the corrected “real” value

· (d) show an understanding of the distinction between systematic errors (including zero errors) and random errors

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

Precision: Small random error

Accurate: Small systematic error

(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: Size of an error and its units

Fractional uncertainty: Absolute uncertainty / measurement

Percentage uncertainty: 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

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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