09 OCTOBER 2019
AS and A Level Physics practicals – student and teacher tips
What are the practical skills required for physics and why do you need them?
The practical skills involved are:
- manipulation, measurement and observation, the collection of simple data to an appropriate accuracy, choosing the right range and distribution of values
- presentation of data and observations in a table
- analysis, conclusions and evaluation, using and justifying the correct number of significant figures
- plotting of a graph and calculation of a gradient. In the second paper this involves the use of logarithms and plotting error bars on graphs
- estimating the uncertainties in measurements made and identifying the most significant sources of uncertainty
- calculating the uncertainty in the value of a calculated quantity made from two or more measurements each with their own uncertainty
- evaluation of the method involved and suggesting improvements
- planning an experiment, including identifying dependent and independent variables and quantities that remain constant, identifying any risks involved
Developing practical skills prepares students for studies beyond A Level in physics, engineering or in physics-dependent vocational courses. Practicals also help students develop abilities and skills that are useful in everyday life and encourage safe practice. These practical skills help to develop attitudes such as a concern for accuracy and precision, initiative, inventiveness and a spirit of enquiry.
These skills are important in employment and go far beyond mere knowledge of facts. A good practical course also helps to develop an interest in the subject of physics itself and complements the study of the theory, showing that scientific theory is ultimately grounded by experiment. The amount of practical apparatus required does not have to be enormous because working within the resources available is another useful ability. It's important to remember that students can learn a lot from practical work that goes wrong as well as from experiments that work perfectly every time.
What are the main challenges for students carrying out practical work?
Many students at A Level may not have had much experience of practical work and may not consider themselves to be very ‘practical’, but there is no need to be afraid of simple experiments. Students need practice in setting up simple apparatus and to be happy in carrying out the experiment by themselves. When a student has enough experience of simple apparatus then they face the challenge of writing a method where they must choose the apparatus and method for themselves. This might be for an experiment that differs from any that they have previously seen and shows their inventiveness and initiative.
Students may also believe practical work to be a mathematical exercise where there is a right and a wrong answer. This is not the case. Every reading has an inherent uncertainty and students need to be happy to estimate uncertainties in simple quantities, such as the measurement of length and time by either repeating readings or taking the smallest scale reading on the instrument used. They also need to realise that the uncertainty is only an estimate and is itself not exactly known.
There are a few mathematical challenges, particularly for those not studying mathematics at A Level. These include the use of logarithms and combining uncertainties, where a real familiarity with percentages is a useful skill. However, the average student can learn the necessary skills with a reasonable amount of application.
What are the main challenges for teachers?
The major challenges are organising the practical apparatus within their school and having sufficient time within a laboratory to undertake enough practical work during the course. Having practical papers in the examination means that schools must budget sufficient resources and laboratory space for their physics A Level students. Teachers must firmly make the case for adequate resources.
Some schools are fortunate to have a technician who is skilled enough to maintain the equipment and provide it at the start of a practical activity. Teachers need to make sure that all apparatus is returned correctly and undamaged, while schools must realise that some damage is inevitable and that the teacher should not be financially disadvantaged.
Teachers need to develop a scheme of work that integrates practical work with theory. This might involve study of uncertainty at an early stage and then its use as the course proceeds. Ideally, there would be a number of simple experiments for each section of the course, not unlike those at O Level or Cambridge IGCSE, but which involve more individual involvement. Teachers need to keep a database of useful experiments that use apparatus readily available and involve experiments that have been used in Cambridge Assessment International Eductation examinations or in the practical workbook.
What are your 5 top tips for students for practical work?
1) Think actively about every topic. Do you understand what is going on? If not, then ask a question.
2) Know how to estimate uncertainty as the smallest scale division or, better, half the range in the readings.
3) After every experiment write down:
- the steps that you actually took during the experiment
- whether each quantity was dependent, independent or kept constant
- major difficulties
4) Realise that readings in a table are measured, usually, to the same precision, i.e. to the same number of decimal places, but that calculated quantities should be given to the smallest number of significant figures in the quantities used in the calculation.
5) Take care when plotting graphs.
- does your graph cover half the page horizontally and vertically?
- does it have units on both axes?
- check your points are accurate
- use a long ruler when drawing a straight line
- show your working in finding the gradient
What are your 5 top tips for teachers for practical work?
1) Make the subject interesting by involving students in practical work from an early stage. Allow the students to discuss their plans, difficulties and improvements, while ensuring that each student can make a significant contribution.
2) Use simple experiments from the practical workbook or from past papers to build student confidence, particularly at the start of the course.
3) Have sufficient practical work built into your course. Many experiments can be made with simple apparatus, e.g. calculate the area and even the volume of a piece of paper and its uncertainty using just a ruler.
4) Give your students a simple guide to all the necessary skills, e.g. how to find uncertainty, how to draw a good graph etc.
5) When apparatus is not available, use the internet or a computer simulation to demonstrate an experiment, but do so while involving students actively, e.g. stopping at intervals and giving students a task: such as to discuss how next to proceed or to write a bullet point account of what has just been done.
By Graham Jones
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