OCR Specification focus:
‘Apply investigative approaches and methods to practical work, including solving problems in practical contexts and planning appropriate procedures.’
Investigative approaches and problem-solving are central to A-Level Physics, requiring students to design, plan, and evaluate experiments methodically, using evidence-based reasoning to understand physical phenomena and refine practical methods.
Understanding Investigative Approaches
In physics, an investigative approach refers to the structured method by which scientists explore questions about the natural world. Students must apply logical, evidence-driven thinking to practical contexts, linking theory to observation. The goal is to form hypotheses, design valid experiments, and interpret data critically to reach sound conclusions.
Investigation: A systematic process involving planning, executing, and analysing experiments to explore physical relationships and test hypotheses.
Investigative approaches underpin every stage of practical physics, from identifying research questions to presenting findings. This subtopic ensures that students can confidently plan and adapt procedures, demonstrating initiative and resilience when faced with experimental challenges.
Stages of Scientific Investigation
A well-designed investigation follows an ordered sequence that mirrors professional scientific practice.
A flowchart of the scientific method, highlighting hypothesis formation, experimental testing, analysis, and iteration. It supports planning procedures and maintaining a logical sequence in practical work. Minor extra elements (e.g., ‘communicate results’) extend but do not exceed the OCR focus on investigative approaches. Source.
1. Identifying the Problem
The investigation begins with recognising a problem or question arising from physical principles. This should be clear, measurable, and capable of being tested experimentally. Good questions often use the structure: How does X affect Y?
2. Formulating a Hypothesis
A hypothesis provides a testable explanation based on existing scientific theory. It predicts the relationship between independent and dependent variables and forms the foundation of experimental design.
3. Selecting Variables and Controls
Independent variable – deliberately changed to observe its effect.
Dependent variable – measured to assess the outcome of changes.
Control variables – kept constant to ensure validity.
Controlled Experiment: An experiment where only the independent variable is altered while all others are kept constant to isolate its effect on the dependent variable.
Maintaining control over variables is essential for producing reliable and reproducible results, ensuring conclusions are based on cause-and-effect rather than coincidence.
4. Planning the Method
Planning involves outlining precise procedures to gather quantitative or qualitative data effectively. A clear method includes:
The apparatus required.
A risk assessment identifying potential hazards.
Step-by-step procedures ensuring accuracy and repeatability.
Appropriate data collection intervals and measurement precision.
When planning, repeatability and reproducibility are prioritised, ensuring that others can replicate results and confirm findings independently.
Problem-Solving in Practical Physics
Problem-solving is the application of reasoning to interpret data, address anomalies, and refine methods. Physics investigations often require critical thinking to troubleshoot issues such as inconsistent readings, apparatus errors, or environmental influences.
Systematic Error: A consistent deviation caused by flawed equipment or method, affecting accuracy but not precision.
Problem-solving involves identifying and compensating for such errors, using theoretical understanding to guide practical improvements.
Analytical Thinking
Analytical reasoning allows students to connect physical laws with empirical results. Effective approaches include:
Comparing results with theoretical predictions.
Identifying sources of uncertainty.
Using graphs to visualise relationships and detect trends.
Evaluating whether anomalies suggest error or new understanding.
Developing Hypotheses and Predictions
A strong investigation is built upon theoretical modelling — applying physical laws to predict expected outcomes. For instance, relationships such as proportionality or linearity can be hypothesised using established formulae.
Hypothesis: A proposed explanation predicting the outcome of an experiment, based on prior knowledge and physical theory.
Predictions allow comparison between expected and observed results, helping determine whether a model accurately describes reality. If discrepancies arise, they can indicate flaws in experimental design or deeper physical phenomena requiring reconsideration.
Planning Appropriate Procedures
A good procedure is logical, efficient, and safe. Students must choose appropriate techniques and apparatus that provide sufficient precision for the task.
When planning:
Select measuring instruments with suitable resolution and range.
Ensure calibration where necessary.
Identify and minimise potential random and systematic errors.
Record environmental conditions that could influence results.
Procedural design also requires considering fair testing, repeat trials, and appropriate data analysis methods such as averaging or uncertainty propagation.
Uncertainty: The range within which the true value of a measurement lies, considering instrument precision and human judgment.
Appropriate procedures are those that maximise data reliability while remaining feasible within laboratory constraints.
Logical Problem-Solving Techniques
When practical difficulties arise, students should follow a structured reasoning process:
Identify the issue by analysing inconsistencies or unexpected trends.
Hypothesise potential causes, considering both equipment and human error.
Test corrections systematically, altering one factor at a time.
Evaluate improvements by comparing revised data to theoretical expectations.
This iterative process mirrors how professional physicists refine experiments and theories over time.
A diagram of an iterative cycle showing repeated planning, action, and evaluation. It visualises how procedures are refined to improve accuracy and validity. Although generic, it maps directly onto experimental troubleshooting in physics. Source.
Iterative Process: A cyclical method of refinement where experimental design, data collection, and analysis are repeated to enhance accuracy and understanding.
Such reasoning ensures investigations are self-correcting and evidence-led, aligning with the empirical nature of physics.
Evaluating and Reporting Findings
Evaluation is integral to investigative work. Students must assess whether their data support their hypothesis and discuss limitations. Important evaluative criteria include:
The reliability and accuracy of measurements.
The significance of uncertainties.
The validity of conclusions drawn.
Recommendations for improving experimental design.
Effective communication of results involves clear presentation using tables, graphs, and units. Findings should be reported objectively, referencing evidence rather than opinion.
Role of Investigative Skills in A-Level Physics
The OCR A-Level Physics course expects students to demonstrate independence, analytical ability, and methodical reasoning. Investigative and problem-solving skills form the foundation for experimental competence, enabling learners to:
Plan and execute complex experiments.
Apply quantitative analysis to interpret results.
Critically evaluate evidence.
Link practical findings to theoretical models.
Through consistent application of investigative methods, students develop both scientific literacy and transferable reasoning skills crucial for university-level physics and research environments.
FAQ
A scientifically valid investigation isolates the relationship between independent and dependent variables by maintaining all other conditions constant.
Validity depends on:
Controlling variables that might influence results.
Using suitable measuring instruments with appropriate precision.
Ensuring repeatability and reproducibility by following a clearly defined method.
A valid experiment produces data that genuinely test the hypothesis rather than being affected by uncontrolled external factors such as temperature, friction, or human error.
Reliability refers to consistency—whether repeating an experiment under the same conditions gives similar results.
Accuracy measures closeness to the true value, depending on instrument quality, calibration, and experimental design.
An experiment can be reliable but inaccurate (if all measurements are consistently off due to systematic error), or accurate but unreliable (if data vary widely from trial to trial). Both reliability and accuracy are required for trustworthy conclusions.
A hypothesis gives direction and purpose to an experiment by predicting an outcome based on established physical laws.
Testing a hypothesis allows students to:
Assess whether existing theories hold true under experimental conditions.
Identify anomalies that may suggest new insights.
Apply logical reasoning to confirm or refute relationships between variables.
Even when disproved, a hypothesis contributes to deeper understanding by refining theoretical models or prompting new questions for investigation.
Typical errors include:
Failing to identify or control all relevant variables.
Choosing instruments with inadequate resolution or inappropriate range.
Not performing repeat measurements to reduce random errors.
Recording data without units or uncertainty estimates.
Students sometimes also overlook safety considerations or the need to calibrate instruments before use, both of which are vital for producing valid and credible results.
Effective problem-solving involves adapting to unexpected results or issues during an experiment.
Students should:
Analyse anomalies by comparing data trends with theoretical expectations.
Identify causes such as faulty equipment, environmental effects, or poor control of variables.
Modify the method systematically, changing one factor at a time.
Document changes and reasoning clearly in their notes.
This demonstrates scientific reasoning and initiative, reflecting the investigative mindset expected in A-Level Physics practical work.
Practice Questions
Question 1 (2 marks)
A student investigates how the length of a pendulum affects its period of oscillation.
State two variables the student must control to ensure the investigation is valid.
Mark Scheme:
(1 mark) Controls amplitude of swing (or angle of release) to ensure it does not affect the period.
(1 mark) Controls mass of the bob or type of string to ensure only pendulum length changes.
Question 2 (5 marks)
A student is investigating the resistance of a wire by measuring the potential difference across it and the current through it.
(a) Describe how the student should plan and carry out this investigation to obtain reliable data.
(b) Explain how the student could use the results to identify and reduce systematic errors in their measurements.
Mark Scheme:
(a) Planning and carrying out (up to 3 marks):
(1 mark) Describes setting up a circuit with an ammeter in series and a voltmeter in parallel across the wire.
(1 mark) States that the wire length or cross-sectional area should be measured accurately and kept constant where appropriate.
(1 mark) Mentions taking multiple readings of current and potential difference, and plotting a V–I graph to determine resistance from the gradient.
(b) Identifying and reducing systematic errors (up to 2 marks):
(1 mark) Recognises possible systematic errors, e.g. zero error on meters or temperature rise affecting resistance.
(1 mark) Explains how to minimise or correct these errors, e.g. by checking instrument calibration, allowing wire to cool between readings, or reversing connections to test for bias.
