Changes in charge, current and potential difference during the charging and discharging of a capacitor are all exponential-type behaviours. Specifically, the current that transfers charge to or from a capacitor (during charging or discharging respectively) is always greatest at first and declines to zero as time increases. During discharging, the charge loss and the drop … Continue reading Charging a Capacitor (analysis)
Uncertainties and Error Bars
Measurements are always uncertain: there is no such thing as a perfectly precise measurement. At the very least, the instrument used will limit the precision of the value but in many cases other factors can introduce even greater variability. It is always the greater of these two numbers (the resolution of the instrument and variability … Continue reading Uncertainties and Error Bars
How high does a spring toy jump?
Determining a spring toy’s jump height is a useful exercise in the application of physics, not only in terms of this specific example but also in highlighting contrasting approaches to answering any sort of physics question. As is so often the case, there are two possible starting points; the first is theoretical whereas the second … Continue reading How high does a spring toy jump?
Revision tips for Paper 3A
It’s a fool’s game to try to predict what will be in an examination paper but… looking back over past years, there are three practicals that have been used very little in Paper 3A and one of those hasn’t appeared since 2020. So, in my opinion, there is a good chance that this year’s paper … Continue reading Revision tips for Paper 3A
How to read Vernier callipers
Having previously discussed micrometers as instruments that some people find tricky to read (see https://physbang.com/2025/04/09/how-to-read-a-micrometer/) we now come to the instrument that many people find even more difficult; Vernier callipers. Whereas micrometers are mostly used for measuring thicknesses between flat surfaces, callipers are better when the surfaces are curved. In particular, callipers are commonly used … Continue reading How to read Vernier callipers
Random and Systematic Errors
Two previous posts covered uncertainties in the context of thermal energy transfers but now we need to consider random and systematic errors as they apply more generally in the current AQA A-Level Physics course. NOTE: The AQA A-Level Physics syllabus takes a simplified approach to uncertainties so if you are doing independent revision you may … Continue reading Random and Systematic Errors
Active Reading
Little is made of the fact that the skills required to read a textbook are different from those used when reading a consumer magazine or a work of fiction. The reasons for this difference are the greater density of information and sequencing of concepts that occur in non-fiction publications. As a result, skimming is best … Continue reading Active Reading
Hypothesis and Analysis
When carrying out a practical investigation it is always helpful to know what sorts of results are expected. In other words, before starting an experiment it is a good idea to consider what theory tells us should be the outcome. The predicted findings form the basis of an hypothesis, which is developed by considering an … Continue reading Hypothesis and Analysis
Experimental Errors (part 2)
The previous post (Experimental Errors, https://physbang.com/2023/11/12/experimental-errors/) ended with an invitation to "consider whether there are any other, previously unidentified, sources of uncertainty" in the method used to derive the specific heat capacity of an iron block. As it happens, there are (at least) three possibilities that weren't covered in the original article. Firstly, there is … Continue reading Experimental Errors (part 2)
Experimental errors
Experiments are often used to confirm (or, more usefully, refute) particular ideas but their impact is limited by measurement errors that can compromise the results. The obvious answer is to reduce the uncertainties as much as possible but what do you do if this causes the result to move further away from the expected value? … Continue reading Experimental errors
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