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Introduction.....................................................................................iv
How to revise most effectively ............................................................................iv
How to be prepared on the day of the exam .......................................................v
Time yourself as follows ...............................................................................v
Things not to do..........................................................................................vi
The layout of the exam paper......................................................................vi
How the questions are marked....................................................................vi
Mandatory experiments .....................................................................................vi
SECTION A – MANDATORY EXPERIMENTS .....................................1
1. Mechanics Experiments: Exam paper question 1 ..........................................2
2. Light and Sound Experiments: Exam paper questions 2/3 .............................9
3. Heat Experiments: Exam paper questions 2/3 .............................................16
4. Electrical Experiments: Exam paper question 4 ..........................................22
SECTION B – THEORY .....................................................................29
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Mechanics .................................................................................................30
Light and Sound ........................................................................................37
Heat ..........................................................................................................47
Electricity – Static, Electric Fields and Capacitance ......................................52
Simple Electric Circuits ...............................................................................61
Effects of Electric Current...........................................................................71
The Force on a Current-carrying Conductor in a Magnetic Field .................78
Electromagnetic Induction .........................................................................84
Semiconductors .........................................................................................91
Electrons, Photoelectric Effect and X-rays ...................................................96
Radioactivity and Nuclear Energy .............................................................109
Option 1 – Particle Physics .......................................................................127
Option 2 – Applied Electricity...................................................................138
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1
Mechanics Experiments
Exam paper question 1
To learn:
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How to describe the mandatory mechanics experiments in points
How to gain maximum marks from the short FAQs that appear towards
the end of many mechanics questions in Section A
How to decide what to graph against what
There are no extra marks for heavy,
overwritten descriptions of an experiment.
There is no need to list the equipment.
This will be clear from the labelled
diagram.
Pay attention to the FAQs, as many marks
are lost here.
Be aware of the importance of
percentage error. If you are
measuring something 10 cm long
and you make an error of 1 cm,
the percentage error is 10%, but
if you are measuring something
100 cm long the percentage
error would be only 1%.
If a question involves a formula, ignore the constants
and you will see what to graph. For example, the
following experiment involves the formula
4π2l
g 2 , so eliminate 4π2 and graph l (Y axis)
T
against T 2 (X axis).
Mandatory experiment
Aim: To investigate the relationship between period
and length for a simple pendulum (and hence to
calculate g)
Method:
1. Attach the pendulum bob to one end of a light thread
and clamp the other end of the thread between two
pieces of cork.
2. Set the pendulum swinging through a small angle and take
the time for 50 oscillations.
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MECHANICS EXPERIMENTS
3. Find the periodic time T for one oscillation.
4. Carefully measure l, the distance from the cork to the centre of the pendulum bob.
5. Repeat for different values of l.
6. Plot a graph of l against T 2. A straight line through the origin implies that l T 2.
The slope of this graph gives the value of l 2 .
T
2
7. g can now be calculated from the formula g 4π 2l
T
FAQs
Why is a light thread used?
So that practically all the mass is concentrated in the bob.
Why must the angle be kept small?
The pendulum formula is only valid for small angles.
Why is the time for one oscillation not measured directly?
It might be too small to register on the timer and there could be a large percentage error.
Why could the number of oscillations be reduced if the length of the pendulum were increased?
Because the time for each oscillation would be increased so the overall time would be
about the same.
How would you ensure that the length of the pendulum remained constant?
Use inextensible string.
Mandatory experiment
Aim: To measure g by free fall
Method:
1. With the switch K in position 1, the ball bearing
is attached to the electromagnet with a small
piece of paper between them.
2. When the switch is thrown to position 2, the
ball bearing is released and the timer T starts.
3. When the ball bearing hits the trapdoor, the timer
stops. The time for the free fall is now known.
4. Repeat a number of times and take the
minimum time, t.
1
5. Measure s carefully. s ut at 2.
2
2s
1
In this case u 0 so that s gt 2 ⇒ g 2 .
t
2
‘g’ can now be calculated.
Note: s should be at least 1 m.
electromagnet
K 1
paper
2
ball bearing
timer T
s
trapdoor
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FAQs
In an experiment to measure g by free fall, give two precautions that should be taken to
ensure a more accurate result.
Measure from the bottom of the ball bearing. Use large values of s (smaller percentage
error). Set the trapdoor as sensitively as possible. Take the shortest time not the
average time.
What is the piece of paper for?
To make sure that the ball bearing does not become magnetised.
Give two ways of minimising the effect of air resistance in the experiment.
Make sure the object is small, spherical, dense, smooth and that there are no draughts.
Using a tickertape timer
A tickertape timer puts a dot on a
s1
s2
tape every 0.02 of a second. If the
tape is moving with uniform
A
B
velocity, the dots are equally
s1
s
u=
v= 2
spaced. However, if the tape is
0.04
0.04
accelerating, the distance between
the dots is increasing. In this case the acceleration can be calculated as follows.
1. Measure s1, the distance over two spaces at the start of the tape. (Taking two spaces
also reduces percentage error.) Now calculate u as above.
2. Measure s2, the distance over two spaces towards the end of the tape.
3. Calculate v as above.
The time t is the time taken to go from A to B.
a (v u)
t
Mandatory experiment
Aim: To show that acceleration is proportional to force
Method:
1. Set up the apparatus as shown in the diagram.
2. Raise one end of the plank until, with a
slight push, the trolley moves with constant
speed.
3. Place a weight in the pan and let the trolley ticker
accelerate down the slope. Note the force F tape
and calculate the acceleration from the
tickertape.
ticker tape
timer
trolley
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Mandatory experiment
Aim: To find the specific latent heat of vaporisation of water
Method:
wet steam
1. Weigh the calorimeter. Weigh
the calorimeter and water. Take
water trap
the temperature of the water.
thermometer
2. Set up the apparatus as shown
in the diagram.
dry steam
3. Allow steam to pass into the
lagging
water in the calorimeter until
copper
calorimeter
the temperature has risen by
about 20° C to 25° C.
4. Finally, re-weigh the
calorimeter and contents to
find the mass of steam condensed.
5. The latent heat of vaporisation of water can be calculated from the equation:
Heat lost by steam heat lost by resulting water heat gained by calorimeter heat
gained by water
FAQs
In an experiment to measure the
specific latent heat of vaporisation of
water:
(a) Why was dry steam used?
To make sure that only dry steam,
and not condensed steam (water),
is added to the calorimeter.
(b) How was the steam dried?
By using a water trap to trap the
condensed steam. It also helps to
insulate the delivery tube and have
it sloping backwards towards the
steam generator.
Remember, most people believe that if you
are familiar with one method of doing an
experiment that is sufficient. This is generally
true but not always! For example, most people
would use the electrical method given above to
find the specific heat capacity of water but take
a look at Question 2, 2007 Higher Level where it
is found by adding hot copper to water in a
copper calorimeter.
(c) Why is the rise in temperature often the least accurate value?
Standard thermometers only read to 1°.
(d) Give two ways of improving the accuracy of this value.
Use a thermometer that reads to 0.1 degrees. Reduce percentage error by using more
steam and less water. Increase insulation.
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HEAT EXPERIMENTS
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(e) Why would a thermometer with low heat capacity increase accuracy?
It would absorb less heat from the water in the calorimeter.
( f ) Why should the calorimeter be polished?
To reduce heat loss by radiation.
(g) How would you find the mass of the steam added?
Subtract mass of calorimeter plus water from the final mass of calorimeter plus water
plus condensed steam.
Exam questions
Q 1: The specific heat capacity of water was
thermometer
found by adding hot copper to water in a copper
loose cotton wool
calorimeter.
(a) Describe how the copper was heated and how
its temperature was measured.
30 g of
copper
A: The copper was heated as shown in the
turnings
diagram and the temperature was read from the
thermometer.
(b) Give two precautions which were taken to
minimise heat loss to the surroundings.
A: Polish the calorimeter, insulate the calorimeter, transfer the copper quickly, use a low
heat capacity thermometer.
Q 2: In an experiment to find the specific latent heat of fusion of ice the following
readings were obtained.
mass of copper calorimeter
50 g
mass of calorimeter water
145 g
initial temperature of water
25° C
final temperature
5° C
mass of calorimeter water melted ice 170 g
Find the specific latent heat of fusion of ice.
A: Specific heat capacity of water 4,200 J kg1 K1
Specific heat capacity of copper 400 J Kg1 K1
Heat gained by
ice in melting
0.025 l
Heat to raise resulting
water by 5° C
(0.025 4,200 5)
0.025l 525 400 7,980
0.025l 8,380 525 7,855
7,855
l
314,200 J 314.2 kJ kg1
0.025
Heat lost by
calorimeter
(0.05 400 20)
Heat lost by warm
water
(0.095 4,200 20)
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4
Electrical Experiments
Exam paper question 4
To learn:
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How to describe mandatory electrical experiments in points
How to answer FAQs on the above
How to get maximum marks from graphs
Mandatory experiment
Aim: To investigate how the current flowing through various conductors
varies with potential difference applied
Method:
1. Set up the apparatus as shown in the diagram.
2. Set the variable resistor to give a small potential difference (voltage). Note the
voltage and the current.
3. Adjust the variable resistor to give a slightly larger voltage. Note voltage and
current again.
4. Repeat 4 or 5 more times.
5. Draw a graph of voltage (Y axis) against current (X axis).
switch
I (mA)
variable
resistor
A ammeter
300
200
tungsten filament bulb
6 V, 0.3 A
resistor
100
V
voltmeter
0
I (A)
I (A)
6
5
1
2
3
4
5
6
V (V)
copper sulphate with
copper electrodes
3.0
4
2.0
Ohmic
conductor
3
2
1.0
1
1
2
3
4
5
5
6
V (V)
0.0
1
2
3
4
5
6
V (V)
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ELECTRICAL EXPERIMENTS
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I (mA)
300
silicon diode
IN 5401
200
100
0.0
0.2
0.4
0.6
0.8
V (V)
At constant temperature the current flowing through a metallic conductor is
directly proportional to the potential difference across it.
This is Ohm’s law.
Not all conductors are Ohmic (obey Ohm’s law).
FAQs
On a graph showing the relationship between current and voltage for a metal at constant
temperature, how would the graph change if the temperature was increasing?
At constant temperature the graph would be linear (Ohm’s law)
I
but as the temperature increased the resistance would increase
and the slope of the graph would decrease to give a curved graph.
In the case of a similar experiment using a filament bulb, why
would the resistance of the bulb change during the experiment?
As the current increases, the temperature of the filament
increases making it more difficult for electrons to pass through.
How would the graph for an ionic solution be altered if the
concentration of the solution was reduced?
Reducing the concentration would mean fewer ions, fewer charge carriers, greater
resistance leading to a reduction in the slope of the graph.
In an experiment to investigate the variation of current with
potential difference for a copper sulphate solution, draw a sketch of
the graph that would be obtained if inactive electrodes were used.
V
I
In an experiment to investigate the variation of current with
potential difference for a semiconductor diode, if the student
changed the diode to reverse bias what changes should be made to
the original circuit?
Replace the milliammeter with a microammeter and make sure
the voltmeter is in parallel with a series combination of the diode and microammeter.
V