Read the bit after the multiple choice about number 8. I explain the working out. How would you approach the question if the length of the wire was 0.2?
No your approach for calculating F = BIlsin(theta) is correct. But 0.2 is the height of the field. The length of the wire in the field is calculated as follows:
I did that AND said that the experiment should be repeated...lol and to assess the reliability, I said to refer to the consistency of results. If results are consistent, it is reliable.
That's only half of the answer. Consistent results does not necessarily mean they are reliable. You could have some fundamental error in your experiment, but it may still yield consistent results, so these results cannot be trusted. Reliability looks are how trustworthy the results and the whole experiment are. One test would be to ensure the experiment was set up according to correct standards and all equipment used were precise for the experiment. After saying that, you can then talk about consistency, repeating results, etc.
+1, OP your 8 is wrong its A
Similar, I would never just say "consistent results", full stop. Considering it was worth 1 mark, then you'll be fine with that answer.
Reliability is about getting results in a small range, isn't it? By removing errors we are removing the size of outliers... Accuracy is how correct the answer is. So we could have ten oscillations but our method could be flawed so accuracy isn't increased. But by minimising the size of errors we could get more consistant and reliable results, because the error from one measurement is not as significant so the errors from all measurements would not be as significant.
http://en.wikibooks.org/wiki/A-level_Physics/Forces,_Fields_and_Energy/Electromagnetism
I don't think this is completely correct. Reliability is indeed a measure of how consistent the results are - even if they are incorrect. Take an archery shooter as an example. Consider someone who never hits the bulls eye, but they consistently shot the number 9, they are a reliable shooter (despite not getting the bullseye). Some one who hits the bulls eye every now and then is considered an accurate shooter, but someone who can consistently hit the bulls eye is considered both RELIABLE AND ACCURATE. Your example about the deformed ruler is deemed INACCURATE, not unreliable.
You need to find the length of the wire that is in the field, you do this by using trigonometry. The length of the wire is perpendicular to the field in the position it is in (despite being at the 30 degree slant), so you don't use the 0.2m length they gave you. The answer is A 1.5A
D94 is definitely not WRONG but the definition of reliability/validity/accuracy seems to vary quite a bit, especially between different fields.
No, I agree, I never said he was WRONG, I said it is not completely correct. I agree with his comment that an experiment that achieves consistent results which are not completely valid (due to wrong experimental method, etc.) is not completely reliable, but for the scope of the HSC I think reliability is defined as the ability to achieve consistent results, whether or not the method is valid.
Your analogy isn't really clear and not the best to compare with my example. A deformed ruler can yield consistent results, so by your definition, it is reliable(?). Sure, reliability is about consistency, however, it must also be trustworthy results (well, they are synonyms of each other). A ruler which is deformed is not trustworthy for this experiment within the reasonable error bounds, hence the results, whilst consistent, are not reliable. Can you really trust results which use a deformed ruler? No. You raised the point about accuracy, but all experiments are not 100% accurate; inaccuracy and unreliability are not mutually exclusive.
Do you have a copy of the exam? look at the diagram, it clearly shows 0.2m is the perpendicular height of the wire. F=BILsin(theta), L is the full length of the conductor in the field, as such we need to use the sin30 & our perpendicular height to find the full length of the wire which is 0.2/sin30 or 0.4.
Reliability in high school terms, is the consistency of the results. No matter how it was performed, valid or invalid, if the results are consistent, it is reliable. By saying whether to trust it or not comes under validity. An experiment may be reliable but not valid. What someth1ng wrote is correct and should get the mark.