ATAR Notes: Forum
VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Physics => Topic started by: sxcalexc on April 26, 2008, 04:13:37 pm
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Hey all, having trouble with this question, which is probably very simple. Our teacher didn't cover diodes and voltage input/output graphs very clearly at all (along with the electronics course so far :buck2:)
(http://img169.imageshack.us/img169/3121/24095385jy4.jpg)
I don't even understand what type of circuit that is, which way is the positive and negative terminal? :-\
Here are the answers, all I need is an explanation of how these graphs were formed.
(http://img166.imageshack.us/img166/7140/94351600yq3.jpg)
Help much appreciated!
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for both of them, there are no definitive positive/negative terminal. the Vin signal is AC in both cases. When it is positive, we'll assume that conventional current flows clockwise. When it is negative, it is in the opposite direction.
Both of these circuits are parallel circuits, with Vout parallel to RL and the diode, and then in series with the resistor R.
Since voltage in parallel circuits are the equal, when the diode is forward biased, the voltage across RL and Vout will both be at the switch-on voltage for the diode, ~0.7V (this applies to both circuits)
This is the case when Vin is positive and greater than 0.7V (i.e. diode is forward biased and conducting), and hence where Vin is greater than 0.7, Vout is capped at 0.7V
When we turn this around, the diode will be reverse biased, and that section of the parallel circuit will not conduct. Since these components are parallel, the reverse-biased diode does not affect the rest of the circuit at all, and can be ignored. what you end up with is a voltage-divider.
In circuit 1, RL is significantly larger than R (10,000 times larger), practically all of the voltage goes through it, hence the bottom peak Vout~-10V
In circuit 2, RL is equal size with R, using the voltage divider formula, we arrive at the bottom peak of Vout=-5V
hope that explains it =)
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Woot! Love the Mao, that helped very much! Call me a nerd but these circuits are actually kinda fun haha ~ I love when stuff works
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Listen use Check points not the book for revision those aren't going to be on the exams by the way i have about 70 exams for physics if any one wants them all i need is a cheat sheet
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Listen use Check points not the book for revision those aren't going to be on the exams by the way i have about 70 exams for physics if any one wants them all i need is a cheat sheet
what do you mean by use checkpoints? checkpoints is just regurgitation of past-exams.... :P
if you could send me the practice exams?? =D
and what do you mean by "all i need is a cheat sheet"?
ps: some punctuations would be nice.
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Checkpoints Physics actually has new questions written in it, and some good notes at the back, rather then just past exams. And I would also like some practice exams lol :P
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And I would also like some practice exams lol :P
Me 2 pease!!! ;D
How did you get so many practise exams?!?!
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70 exams... that's awesome.
Could I be added to the list! :)
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I got a load of physics practise exams too.
MSN me for them :)
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How much do we actually need to know about modulation and optical fibres?
The Nelson textbook is a bit vague.
Thanks.