Accuracy, Precision, Error and UncertaintyThis 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.
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.
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.
Using Micrometers and Calipers
How do you actually use a micrometer to measure small distances?
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.
Parallax Error and how to minimise it
Parallax Error - What it is and how to minimise it. Simple.
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.
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.
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.
Percentage Uncertainty in Single Measurements
Percentage uncertainties for single measurements can be calculated using the equation in this video.
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.
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).
Percentage Difference
Percentage difference' gives an indication of how close your experimental value is to the accepted true value.