P2 Controlled Assessment
How the resistance of an LDR
changes with the brightness of a
lamp
The controlled assessment is
internally assessed and forms
25% of each GCSE in science.
Controlled Assessments (CAs)
Controlled assessments are been split into three parts:
Part A
Part B
Part C
Planning
Observations
Conclusion
(limited control)
(limited control)
(high control)
You will need to complete all three.
E.g. The plan in part A is used to collect the results for part B and for the
conclusion in part C.
Part A
Planning
(limited control)
For GCSE Science you will be given an
hypothesis (a scientific idea to be
investigated). You will then have to
carefully plan how you will test the idea.
20 marks
Rules:
 You are allowed to work groups/ teams to discuss ideas etc
 When planning you can have access to your class notes.
 You may be allowed more than one lesson to finish your plan.
 However you must write up your plan individually in class under
teacher supervision..
 When finished your teacher will check your plan. Your plan cannot be
changed once it has been checked.
If your plan is deemed as dangerous, your teacher will give you a
suggested plan, but no marks can be awarded.
Rules:
Limited control.
 You can work in groups/teams during experimental work to discuss
ideas and to generate results.
 However you must write up and record your own data/ evidence.
 You will also need to collect and record secondary evidence to support
the hypothesis and comment on the quality of the source. (Best to use
another groups/students results plus your own internet research)
24 Marks
Rules:
High control – this must be completed individually under the
supervision of your teacher. This can take place over several lessons but
your work must be collected in at the end of each lesson.
 Can collect evidence for homework.
 Must be your own work.
 Absent pupils, will be given results – no marks awarded for data.
P2 Year 11 Controlled Assessment
To put it simply!
• Your are going to change the voltage, this will
increase the current and make the bulb
brighter.
• You will then see how this effects the
resistance of the LDR.
Current is a measure of the rate of flow of electric charge
through a circuit. A large current means that the rate of
flow is more rapid.
Current can be changed by increasing or decreasing the
voltage of the circuit.
Resistance is a measure of how
hard it is for electrons to move
in an electrical circuit. The
higher the resistance the
harder it is for the current to
flow.
• Current is measured using in Amps using an
ammeter.
• Voltage is measured in Volts using a Voltmeter.
• Resistance is measured in Ohms using an
Ohmmeter.
Light Dependent Resistor
How it works
Light Dependent Resistor
• The most common type of
LDR has a resistance that
falls with an increase in the
light intensity falling upon
the device (as shown in the
graph). The resistance of
an LDR may typically have
the following resistances:
• Daylight= 5000 ohms
• Dark= 20000000 ohms
What’s the point in LDR’s
• To put it simply they are just automatic on/off
switches. One every day us of them is in street lighting.
During the day the resistance is low so the current has
too paths.
What’s the point in LDR’s
• During the night the resistance of the LDR is
very light so all the current will flow through
the bulb.
Hypothesis
4 Marks
• How will the brightness of the light effect the
resistance of the LDR?
• Key things to remember• The current is a measure of brightness.
• This will then effect the resistance of the LDR.
Equipment (2 Marks)
• What equipment do you think you are going to
need? This should be a list with explanations for
why you need each thing. Below are some
examples.
Resistance is measured in Ohms using
an Ohmmeter.
Current is measured using in Amps
using an ammeter.
Light dependent resistor will detect
light and vary in resistance.
A thermistor will detect temperature
and vary in resistance.
Voltage is measured in Volts using a
Voltmeter.
Controls
• In any scientific experiment we have 3 things:
• Independent variable- The thing we change
• Dependent variable- The thing we measure
• Controls- The things we keep the same.
What are our independent and
dependent variables?
Controls
• The things we keep the same to ensure valid
results.
Ideas for
Controls
Controls
6 Marks!
• To get the full marks in this section you must
identify the control, how you will control it
and explain why it needs to be controlled.
20
Min’s
Risks
4 Marks
10
Min’s
• Should be in a list!
• Identify the risk, describe what the risk could
do to you and explain how you will manage
this risk.
Writing a Plan
Add flour, eggs and
backing powder to a
bowl. Mix this up and
put in a baking tray.
Once this is baked add
your icing sugar and
then leave to set.
Could Ernie the
Elf make the
cake for Lenny
the lepricorn
with this recipe?
What’s Wrong with it?
• All in one big paragraph.
• Does not mention how long to do anything
e.g. bake the cake.
• Does not mention the amounts required of
each thing.
• Just like a recipe your plan needs to be
ordered and in detail!
• Assume the person reading it knows nothing
about the experiment.
• Remember as a scientists your plan should be
good enough so that anyone could follow it
and conduct your experiment.
Writing your Plan
Hints and Tips
20
Min’s
• Write it as a numbered list.
• You can draw a labelled diagram of your
apparatus.
• Explanation for how your plan will test your
hypothesis.
• Justify your use of a particular range of
voltages on the powerpack.
Primary Evidence
4 Marks
• This section just involves recording your data
in an appropriate table
• This table should include all your results,
including your repeats.
• The table must have appropriate headings and
units.
Surface
Force (N)
Reading 1
Force (N)
Reading 2
Average
(cm)
Spot the
mistakes in
this table
Secondary Evidence
• This is an extra piece of information which can be
used to help back up your results.
• REMEMBER YOU MUST DESCRIBE WHERE THE
PIECE OF SECONDARY INFORMATION IS FROM
AND ITS CREDIBAILITY.
Credability- Whether the information can be
trusted (if you have taken it from wikipedia then
it cannot!) and how well it relates to your work (if
its the same experiment then its perfect!).
Processing Evidence
(4 marks)
• One you have collected your information you
now need to process it.
• All this means is you need to need calculate
your averages and plot an appropriate graph.
Important point- Before you can do any this you need
to check you results for anomalies, because you will
need to discount these when calculating averages.
Quality of Evidence
4 Marks
• In this section you need to discuss the quality
of all your evidence.
• What makes a piece of scientific evidence
good quality?
Quality of Evidence
4 Marks
• Anomalies- have they been dealt with? How?
Why? In both primary and Secondary
Evidence
Important point- if there are no anomalies you
need to state THERE ARE NO ANOMOLIES IN
MY PRIMARY/SECONDARY EVIDENCE
Conclusion Based on Evidence
6 Marks
• We have successfully
completed a scientific
investigation!
• Have we proved or
disapproved out hypothesis.
Conclusion Based on Evidence
6 Marks
Height of bounce (m)
2.0
1.5
1.0
0 .5
• Lets use an example to help us to do
this!
x
x
x
0
1
2
3
Height of ball off ground (m)
My hypothesis is ‘The
higher the ball is
released the higher
the ball will bounce’
Explain if this
hypothesis is correct,
using evidence to back
up your ideas.
What's expected from you
• Draw conclusions in reference to your hypothesis, did it work
out how you expected?
• You need to use all your results (table and graph) to back up
your conclusions, both your primary and secondary!
• e.g. The ball bounced higher when it was released at an
increased height. My results show that when it was released
at 1m it bounced 10 cm compared to when it was released at
1.5m where it bounced 25cm....... etc
• Explain your conclusion using scientific knowledge. If there
was a pattern, explain why you think there was, if there was
no pattern, explain why there was no pattern.
• e.g. The ball bounced higher when it was released at an
increased height because the it had more gravitational
potential energy..... etc
Conclusion Based Evidence
Structure
Opening Sentence describing if your results had proved
or disproved your hypothesis.
Back up your opening sentence with various pieces of
evidence from your secondary and primary evidence.
Explain your conclusion using scientific knowledge.
Evaluation of Conclusion
4 Marks
• You are now making judgements on the quality of
your conclusion and suggesting methods by which
you could extend it to support it further.
• e.g. Both my primary and secondary data show
similar results, to improve my experiment I could
have released the ball at more heights, this would
helped me further prove whether the height it was
dropped affected how high it bounced..
Evaluation of Conclusion
4 Marks
Do both the primary and secondary evidence give the
same conclusion?
Explain how your evidence can be improved and extended
to better support your conclusion.
Evaluation of Method
6 Marks
• Now we are making judgements about the quality
of our method, it was good, but was it perfect?
• Explain various strengths of weaknesses of your
method. These should be linked to your
hypothesis.
• Make and justify various suggestions to improve
your method and explain why this would result in
stronger quality of evidence and therefore better
prove or disapprove your hypothesis.
Evaluation of Method
6 Marks
Describe various strengths of your method, you need to link these
to your hypothesis. Why did these things ensure you could test
your hypothesis.
Describe the various weaknesses of your method. You could use
these to explain your anomalous results.
Suggest and justify improvements to your method. These could be
linked to your weaknesses. Explain how these improvements could
have better tested your hypothesis.