Practical Skills
A lot of this you already know, but there are quite specific ways to deal with errors and uncertainties at A Level.
There is a lot here: from how the scientific process works, variables, techniques, errors and so on. Have a look as this is really important across all of the course.
Accuracy, Precision, Error and Uncertainty
This video introduces some of the essential terminology you need to understand as you complete practical work at A level for Physics, Biology and Chemistry. This is essential if you are working towards the Practical Endorsement and for your end of year exams where you are assessed on your knowledge of the scientific method.
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Absolute Uncertainty
This video looks at 'Absolute Uncertainty' which is really important as you complete practical work at A Level for Physics, Biology and Chemistry.
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Percentage Uncertainty in Single Measurements
Percentage uncertainties for single measurements can be calculated using the equation in this video.
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Percentage Uncertainty in Multiple Measurements
When you take repeated measurements you need to work out the percentage uncertainty in a different way. The range of the results in now important - the greater the spread of results the less certain you are with your final value.
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Percentage Uncertainty in Gradients
You could be asked about this in your exams. Learn more about the 'lobf' and the 'walobf' in this video (not proper physics terms).
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Combining Uncertainty
You can calculate the percentage uncertainty in the various measured values when you complete practical work for A Level Physics. Combining uncertainties needs extra care. This video shows how to combine uncertainties (adding uncertainties together) to give the final uncertainty in a calculated value.
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Combining Uncertainties - Worked Example
This is a worked example on combining uncertainties for A Level Physics. I record some data, calculate the various percentage uncertainties, then combine these and show you how to find the total uncertainty in the volume of a rod.
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Percentage Difference
'Percentage difference' gives an indication of how close your experimental value is to the accepted true value.
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The Scientific Community
What do real scientists actually do? This is a very brief (and simplified) summary of the scientific process.
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Variables
This is a recap of the variables that you will have used at GCSE. The ones you decide to change, what they have an effect on and also what you need to control to ensure a fair test.
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Control Variables, Fair Tests and Causation
An ideal experiment should have just one variable altered while everything else is controlled. This allows you to collect repeatable and reproducable results that allow you to see the link between two separate factors.
Common Control Variables
You will have to design your own experiments at A Level. This is a brief summary of some of the key variables you should control to allow a fair test.
Anomalous Results
Sometimes a result doesn't fit the pattern - this is an anomolous result and there a couple of ways you can deal with one of these. Either discard it from your calculations or identify it on your graph.
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Results Tables
You have to know how to present your data in an appropriate manner. Get it right from the start and your practical experiments will be a breeze.
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Results Tables for Log Values
A bit of a weird one this, and something that isn't immediately obvious. This is how to deal with log or ln values in your results tables.
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Drawing Graphs
You must be able to draw a graph: to show the relationship between two quantities and then to work out physics constants. In this video I show you the correct choice of scales, the labels and also the way to draw in a perfect line of best fit.
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Gradients and y-intercepts
y = mx + c is the most important equation you should be familiar with. But how do you calculate the gradient? What working should you show? And how do you find the y-intercept if you can't read it directly off the graph?
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Using Micrometers and Calipers
How do you actually use a micrometer to measure small distances?
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How to Read a Vernier Scale
How to use a micrometer is something that you may find useful at some point when measuring small distances. Reading a vernier scale takes patience but once you get the hang of it is isn't so bad.
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Zero Error
Zero Error doesn't mean there is no error. But these can add a systematic error to your readings. Easy to solve using one of two methods.
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Light Gates and Data Loggers
Light gates. Straight forward sensors you attach to a data logger and computer to record the time the IR/visible light beam is broken for. You can then calculate the velocity from these readings.
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Ticker Timers
A ticker timer can be used to investigate the velocity of an object. A 50Hz supply makes a dot every 0.02 seconds on the tape. As this is pulled through the machine it leaves a series of dots. You could then work out the velocity of the object since you know the distance traveled and the time between marks. So simple even small children can understand!
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How to Use a Multimeter
So many students struggle with how to use multimeters at first. In A Level Physics you'll need to be comfortable with using a multimeter. By turning the dial you select what you're measuring and the range of values it is sensitive to. That's it!
How to Prepare for Practical Exam Questions
Want to know how to prepare for questions on practical experiments in A Level Physics? Well, look no further than this video. I go through a check sheet that you can apply to most A Level Physics practical experiment questions that'll help you get the most marks possible.