General
Advice
• There
is no escaping it; thorough and careful revision is the best way to prepare for
a
physics
examination.
• Make
your revision productive by making it interesting and fun. Make notes, revision
cards or
mind maps. Revision should be an active process, i.e. you should be ‘doing
things’,
not just sitting and reading a book.
• Do
not try to learn it all in one go! Take regular breaks and review what you have
learnt
regularly.
• Learning
equations is essential; put them on small pieces of paper and stick them on
your
mirror so you will see them every morning, then revise with a friend so you can
test each
other.
• Try
explaining the physics of a topic to a friend – as if you were a teacher!
• Working
through past paper questions is then the best way to complete your revision.
This helps
you to know the type and style of questions to expect in the examination.
• Try
timed questions so you can learn to answer quickly.
• Make
sure you get your answers checked so you know you are doing the right things!
Spelling
The
spelling of technical terms is important, so make sure your writing is legible
as well
as spelt
correctly. Some words are very similar, such as reflection and refraction.
If the
examiner
cannot tell which one you have written, then you will lose the mark. Make a
list
of technical
terms and definitions in each section of the syllabus, checking the spellings
carefully.
General
Tips
In O Level
Physics examinations you have to be able to complete a variety of tasks;
always
read the question carefully to make sure you have understood what you are
expected
to do.
In
descriptive answers, you should:
• check
the number of marks available and make sure you give sufficient points.
• plan
your answer first so that you don’t repeat yourself or contradict yourself.
• read
your answer through carefully afterwards to check you have not missed out
important
words.
• use
sketches and diagrams wherever you can to help your explanation.
• add
labels when referring to a diagram, e.g. point X, so that you can refer
to it
easily in
your explanation. This can save many words and much confusion.
In
numerical answers, you should:
• quote
any formulae you are going to use.
• show
clearly all the steps in your working.
• check
the units are consistent, e.g. if the distance is given in km and the
speed in
m/s, then you
must convert the km to m.
• be
careful when you are converting minutes and seconds: 1 minute 30 seconds is
not 1.3
minutes and 150 seconds is not 1.5 minutes. These are common
mistakes,
so always double check any conversion of units of time.
• state
the answer clearly at the end.
• give
your answer as a decimal to an appropriate number of significant figures
unless
specifically asked to give the answer as a fraction.
• check
that you have given the unit on your final answer.
• look
at your final answer and see if it is reasonable. If you have the cost of using
an
electrical appliance such as a kettle used for six minutes as more than a few
cents,
then check the powers of ten in your calculation.
Plotting
graphs can be tested in Papers 2 and 3. When drawing graphs, you should:
• remember
to label the axes with both quantity (e.g. distance or d) and
unit (e.g.
metres or m).
Then write it as distance / metres or even just d / m.
• make
sure the axes are the correct way round. You are usually told, for example,
to plot
distance on the x-axis, so make sure you know that x is the horizontal axis!
• make
the scales go up in sensible amounts, i.e. not 0, 3, 6… or 0, 7, 14 … but 0,
5, 10 … or
0, 2, 4 ….
• make
sure that the plotted points fill at least half the graph paper. (This means
you cannot
double the scale and still plot all the points on the graph.)
• check
if you have been told to start the scales from the origin. If not, then think
carefully
about where to start the axes.
• use
a sharp pencil to plot the points and draw the line.
• plot
the points carefully. It is best to use small neat crosses. Every point will be
checked by
the marker, and you will lose the mark if any are wrongly plotted.
• draw
either a straight line or a smooth curve. In physics we never join the dots!
• remember
that a best fit line (curve or straight) should have some points both
above and
below the line.
When
taking readings from a graph, you should:
• draw
a large triangle when measuring the gradient of a line. It must be at least
half the
length of the line. Examiner’s tip – draw a triangle the full size of the
graph!
• always
use points on the line, not your plotted points, when calculating the
gradient.
• draw
a tangent to find the gradient of a curve. Make sure it is at the right place
on
the curve.
Again, use a large triangle.
• make
sure you read the scales correctly when reading a value from a graph. It
may be
that they are in mA rather than A or km rather than m.
When
describing the shape of a graph, remember that:
• directly
proportional means a straight line through the origin. In this
case,
doubling
one quantity will cause the other to double.
• if
the straight line does not go through the origin, then it is just called a
linear
graph.
• if
doubling one quantity causes the other to halve, then they are inversely
proportional.
• if
increasing one quantity causes the other to decrease, it is called an inverse
relationship.
Paper 1
Tips: Multiple Choice
When
reading the question, you should:
• read
the question carefully, e.g. if a question refers to a cooling liquid, then it
will
solidify,
not boil. If you know you tend to jump to a quick conclusion, cover up the
answers
while you read the stem of the question.
• not
rush through the questions. Some will be very quick to answer, others take
more time.
• check
whether a positive or negative answer is being asked for, i.e. does the
question
say “which of the following is or is not …?” For example, when
looking at
ray
diagrams it is easy to just spot a correct diagram when you are asked for an
incorrect
diagram.
• underline
or circle important information in the stem of the question.
• never
leave a question unanswered; marks are not deducted for incorrect
answers.
• try
to eliminate some of the possible answers if you are not sure of the answer.
• write
out your working to numerical questions clearly (on the question paper, near
the
question) so you can check it later.
• be
aware of the topics which occur frequently, such as potential difference and
potential
dividers.
The theory here just has to be learnt!
When
taking readings from a diagram, you should:
• check
you are using the correct distance, e.g. in moments questions, remember
you need
to use the perpendicular distance from the force to the axis of rotation.
• draw
on the diagram to help you understand what is happening, e.g. in a travelling
wave
moving to the right, draw in the new wave outline after a short time, or in
deciding
the direction of the magnetic field at a point near a bar magnet, draw in
the shape
of the field.
Choosing
the right response:
• When
several answers seem correct, re-read the stem of the question. You must
choose the
answer that is not only a correct statement, but also answers the
question,
e.g. swapping the live and neutral wires in a plug is a fault, but will not
cause the
fuse to blow. The live wire touching the metal case of a kettle is a fault
which will
cause the fuse to blow!
Choosing
the right equation:
• Many
equations are very similar, e.g. E = mc2 (energy
equivalence of mass) and E
= ½ m v2 (kinetic
energy of a moving object) so make sure you know when to use
each one.
Paper 2
Tips: Structured Questions
• Read
the stem of the question to check which topic in physics is being tested. Then
read all
the parts of the question. It is often tempting to write too much in the first
part
of the
question and then realise you have answered parts two and three as well.
• Only
answer the question asked. Don’t be tempted to give more detail than is
required.
This wastes time and gains you no extra marks!
• If
you are asked for two points (e.g. name two materials that are magnetic ….)
then
don’t give
three. If you give three and the second is incorrect, you will only get one
mark out
of two.
• Your
answer should fit the space available. If it doesn’t, you are writing too much!
The number
of lines given is a clue as to how much to write. Think about the size of
your
writing: if it is too big, it will not fit in the space; if it is too small,
then the examiner
will not
be able to read it. Practice writing a size that is in between the extremes!
• If
the question asks you to describe the movement of electrons, then not
mentioning
electrons
and only referring to the movement of charged particles in the answer
cannot
gain full marks. Failure to give sufficient detail is a common cause of lost
marks
• If
describing the motion of molecules in a liquid then linking the temperature to
the
average kinetic
energy of the molecules is important. Molecules of a gas exert a
pressure
on the walls of a container by colliding with the walls. To increase the
pressure,
they must collide at a greater rate, i.e. more frequently or with a higher
speed.
Take care to explain this clearly and without contradiction!
• Electrical
circuits are common questions. Make sure you know where to put
ammeters
and voltmeters in a circuit. Then, if you need to vary the current, make
sure you
include a variable resistor or use a variable power supply.
• If
the question asks you to”state and explain” you need to give a clear
explanation.
The amount
of detail depends upon the number of marks for the question, e.g. if the
direction
of the current in a solenoid is reversed, then just saying that the magnetic
field
changes is not enough. This could mean increases or decreases in strength.
You need
to state that the field reverses or changes direction.
• Make
sure you link your answer to the question, rather than just quote learnt facts,
such as
the penetration of radioactive radiation. Just stating what stops alpha, beta
or gamma
will not gain all the marks.
• If
you are asked to draw forces on a diagram, be sure to draw them through the
point
where they
act. Do not draw them floating in mid-air to the side of a diagram!
Remember
to label them. Make sure you add an arrow to show the direction, e.g. if
the
question asks for “the force exerted by the Sun on the Earth”, then since it is
a
force of
attraction, the force arrow must go from the Earth towards the Sun.
• If
you are asked to draw a forces diagram, make sure the diagram is large enough,
and that
all the forces are drawn with arrows and labelled.
• Where
a question asks for a formula to be quoted, there will be one mark specifically
for this.
Even if you get the right answer, failure to quote the formula will lose you a
mark.
Some
incorrect physics statements will lose a mark even if followed or accompanied
by a
correct
statement. Examples of such statements are:
• Renewable energy sources can be used again and again. Please
use the
explanation
that there is an infinite supply or it will not run out.
• Heat rises. Note that it is either hot air or
hot liquids that rise, carrying the heat
energy
with them.
• Acceleration at a constant speed. This is
a contradiction as if travelling at a
constant
speed, you cannot be accelerating! When describing a uniform
acceleration,
you can say constant acceleration or that it is accelerating at a
constant
rate.
Paper 3
Tips: Practical Test
• You
will have three short experiments (20 minutes each) and one longer experiment
(1 hour).
• Read
the instructions carefully. Make absolutely sure you know exactly what you are
asked to
do each time.
• You
do not have any time to waste, so you need to be sure you are doing the right
thing
first time.
• Write
down all your readings clearly in the answer booklet.
• When
asked to take a single reading, make sure you include the unit.
• Do
not write anything you are not asked for – you are not expected to write an
account of
the experiment.
• If
you are asked to “use your results” to explain something, then quote them, not
just
use the
theory you know!
• Think
about the experiment as you do it – you are often asked for sources of error or
difficulties
you met while doing the experiment. Make sure you give sufficient detail,
e.g. don’t
just say "to avoid parallax error” but say how this is avoided. This can
be
done by
drawing a suitable diagram showing the position of the observer relative to
the scale.
• Significant
figures are important in the practical papers. Do not quote too many – or
too few!
Just right is important.
• If
you are reading a measuring instrument, give all the values on the scale, e.g.
on a
hundredth
of a second stopwatch, write 9.24 s (but not 09:24 s).
• Many
marks are lost by giving too few significant figures. This usually occurs when
reading a
scale where the value is on a major mark, e.g. 6 V. If the scale
measures
to 0.1
V, then the reading is 6.0 V, and you must include the point zero!
• In
calculated values, you should give the same number of significant figures as in
the
values
used, e.g. the average of 27.95, 26.54 and 27.36 is 27.28333333 and should
be given
as 27.28.
• Make
sure you understand the technical terms used in the question, e.g. extension
means the increase
in length of a spring when a load is added.
• When
measuring vertical heights, a setsquare should always be used to ensure the
ruler is
vertical. The setsquare should be shown correctly positioned in the diagram.
When you
have completed an experiment, go back over your answers and:
• check
that you have answered all the parts of the question. Read the instructions
again. You
may be asked to draw a diagram after a calculation and this can
easily be
missed.
• check
that you have read scales to the correct power of ten, e.g. when reading an
ammeter
should it be 0.012A, 0.12A or 1.2A?
• check
that you have the correct number of significant figures.
• check
that you have added a unit to all your measurements and any calculated
values,
and then check that it is the correct unit!
In the
Section B question, you will be asked to take a set of readings to plot a
graph.
When
recording your readings in a table:
• Write
both the quantity and unit in the heading. Note that the quantity means
current,
not "reading on the ammeter”. Don’t write the unit after every reading in
the table.
This just clutters up the table and makes it difficult to see the values
clearly; a
heading should say current / ampere or just I / A.
• You
do not need a column labelled”reading number” which just goes 1, 2, 3 etc.
If
you are
given a table outline in which to record your results, this will use one of
them and
you will not have enough columns for your results.
• Make
sure you have taken sufficient readings, e.g. if you are asked to measure
the
temperature of a cooling liquid for five minutes, then a reading every minute
gives you
too few readings. Every 30 seconds is acceptable.
• Make
sure you record the temperature for the full time.
• Don’t
forget to note the initial temperature when you start the stopwatch.
• If
using a liquid in glass thermometer, you should be able to estimate within a
degree,
e.g. to 0.5oC or even
0.25oC.
