ATAR Notes: Forum
VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Physics => Topic started by: Uberjew on November 06, 2013, 12:50:09 am
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Hey guys,
Just wondering if we will be awarded full marks for using a negative answers for the voltage gain of an amplifier if it is inverting.
Thanks
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Not sure about full marks for having the negative there, but I know in previous reports they've said you do get full marks for not having it there, to be safe I always include magnitude signs when calculating the gradient so I end up with a positive answer, and I know that gives full marks. I can't see them taking a mark off for the negative, but the reports don't have it there so why take the risk?
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but the reports don't have it there so why take the risk?
I'll keep doing more exams and see their trend but I know some 2013 commercial exams have stated that full marks are *only* given if a negative sign is included... not sure what to do so far :(
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I thought inverting amplifiers were taken off the course?
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It should only be positive though just because the gain is a MAGNITUDE so you can't have negative. I don't think you will have marks taken off you since they are only 2 marks question generally
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But they define "gain" as "output voltage" divided by "input voltage", or the slope; no mention of magnitudes anywhere.
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But they define "gain" as "output voltage" divided by "input voltage", or the slope; no mention of magnitudes anywhere.
Hmm, this is getting fairly into the semantics of the wording. The textbook states that it's a ratio between the two voltages, I have read somewhere that it is meant to be just the magnitude (could be the ATAR notes book) but I think due to this ambiguity they will simply mark both as right. I think the safest way to do it would be have the negative value in the working out answer but have it positive in the box. If it is only meant to be positive, then your fine but if it's meant to be negative, they will assume a transcription error have occur
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Last year's exam 1 report attached,
The voltage gain was the magnitude of the gradient, which was 250. Negative 250 was also acceptable.
I knew it was somewhere
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VCAA are not strict on this and they will pay you the mark,
nevertheless my teacher said you always find the absolute value of your answer...
Thus always positive.