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March 29, 2024, 09:09:02 pm

Author Topic: VCE Physics Question Thread!  (Read 603546 times)  Share 

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lzxnl

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Re: VCE Physics Question Thread!
« Reply #210 on: October 07, 2013, 06:12:34 pm »
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I've seen those questions before in past exams. Given the cutting of the physics course down, it's possible that you're not asked to know this.

In case you do, something on the lines of the thermal vibrations of the electrons creates an electromagnetic wave, light, would probably suffice.
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barydos

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Re: VCE Physics Question Thread!
« Reply #211 on: October 07, 2013, 06:30:28 pm »
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I've seen those questions before in past exams. Given the cutting of the physics course down, it's possible that you're not asked to know this.

In case you do, something on the lines of the thermal vibrations of the electrons creates an electromagnetic wave, light, would probably suffice.

Thanks nliu :)
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Re: VCE Physics Question Thread!
« Reply #212 on: October 07, 2013, 09:00:34 pm »
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how do you do question 8 from electronics section.
http://www.vcaa.vic.edu.au/Documents/exams/physics/2009physics1-w.pdf

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lzxnl

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Re: VCE Physics Question Thread!
« Reply #213 on: October 07, 2013, 09:12:54 pm »
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OK. P is definitely an electric signal as that's what microphones do; convert a sound signal into an electric one. I would say P is B.

It looks to me that Q, the wave from the RF source to the modulator is the carrier wave, high frequency, so A is at Q. Then R appears to be the modulated wave signal C. S is the original electric signal B.
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SocialRhubarb

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Re: VCE Physics Question Thread!
« Reply #214 on: October 07, 2013, 09:16:50 pm »
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The process of modulation involves varying the properties of a wave in order to transmit information.

So in this case we're transferring the sound coming through the microphone on the back of a radio wave.

Into the question now:

at P, all that we have is the signal from the microphone. It's a sound wave which has been converted into an electrical signal, and the other waves which we're required to label are radio waves. In general, the frequencies of light, even in the form of radio waves, will be much higher than the frequencies of sound. So if we're trying to pick a waveform which will match the sound, we'll probably pick B, as its frequencies seems the lowest.

At Q, all the we're receiving is the 'carrier wave', the wave that will be altered to carry the sound wave. In this case it is a radio wave. The wave hasn't yet reached the modulator, so what we're looking for is a flat, uniform wave, which in this case will be A.

At R, the wave has been altered to carry the signal. The answer will be C, as you can see that the waveform has been altered to 'carry' the original sound sample on top of the radio waves being emitted. You can imagine that if you multiplied the waves in A and B together, you might get something that looks like C.

At S, the wave has been demodulated to form the original electrical signal from the microphone, so we're back to B again.
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Jaswinder

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Re: VCE Physics Question Thread!
« Reply #215 on: October 07, 2013, 11:48:28 pm »
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is there a difference between cut off potential and cut off voltage? can the cut of potential have eV units?

Robert123

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Re: VCE Physics Question Thread!
« Reply #216 on: October 10, 2013, 06:48:59 pm »
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Photonics (detailed study) question,
Could someone please explain the what "numerical aperture" and "acceptance angle". I can usually get MC questions related to them right by applying the formula but I have no genuine idea what the numbers even mean.
Cheers

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Re: VCE Physics Question Thread!
« Reply #217 on: October 11, 2013, 07:11:57 pm »
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To nliu and Alwin and potentially others, I got my hands on the VCE Physics Exam marking principles today. No working, correct answer = full marks regardless of number of available marks.

Some other absolute gems:
"If the student changes the units in the answer box and his answer is correct, give full marks."
"Scientific notation – 2 E 9 is acceptable"
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BasicAcid

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Re: VCE Physics Question Thread!
« Reply #218 on: October 11, 2013, 07:22:21 pm »
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Some other absolute gems:
"If the student changes the units in the answer box and his answer is correct, give full marks."
"Scientific notation – 2 E 9 is acceptable"

Wow are you serious lol

Do you think you could link us/post the marking principles?

sin0001

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Re: VCE Physics Question Thread!
« Reply #219 on: October 11, 2013, 07:33:05 pm »
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To nliu and Alwin and potentially others, I got my hands on the VCE Physics Exam marking principles today. No working, correct answer = full marks regardless of number of available marks.

Some other absolute gems:
"If the student changes the units in the answer box and his answer is correct, give full marks."
"Scientific notation – 2 E 9 is acceptable"
So if there are 3-4 marks devoted to a question, we can full mark it simply by writing the answer? Source please.
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~T

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Re: VCE Physics Question Thread!
« Reply #220 on: October 11, 2013, 07:55:33 pm »
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Definitely not me asking here... it's um... for a friend... um... can you upload documents here?  :P

http://www.2shared.com/document/0BRMUi2k/General_marking_principles.html

P.S. Enjoy <3

P.P.S. I believe this was from the chief examiner during a 2012 teachers conference
« Last Edit: October 11, 2013, 08:25:03 pm by Tim...blahhh »
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Phy124

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Re: VCE Physics Question Thread!
« Reply #221 on: October 11, 2013, 08:18:11 pm »
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So if there are 3-4 marks devoted to a question, we can full mark it simply by writing the answer? Source please.

Why would anyone put just an answer when there are multiple marks allocated?

If you get the answer wrong and have no working out, then you get zero, it's as simple as that.

However, if you have the incorrect answer but have working out is certainly possible to obtain marks.

In a subject where you hear numerous stories of people mistyping things into their calculators and obtaining an incorrect final answer, I really don't understand why you would simply write an answer and nothing else, especially considering it takes, what, an extra 5 seconds to write?  ???
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~T

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Re: VCE Physics Question Thread!
« Reply #222 on: October 11, 2013, 08:29:10 pm »
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I certainly agree. I was merely clarifying as it was seemingly debated earlier without any resolution. I would always do working if (almost always) I have the time, but you must admit that you occasionally get a two mark question - say, finding the current in a simple circuit - and if you happen to have stuffed up something earlier, and spent too much time fixing it or blanking on a question and find yourself under the pump, it's nice to know that you will still get the full marks IF the answer is right. To do so in a 4 mark question would of course be ridiculous, but it's also nice to know that you don't have to show a huge amount of steps if you are confident. Again, not saying I would.
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sin0001

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Re: VCE Physics Question Thread!
« Reply #223 on: October 11, 2013, 09:57:51 pm »
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Why would anyone put just an answer when there are multiple marks allocated?

If you get the answer wrong and have no working out, then you get zero, it's as simple as that.

However, if you have the incorrect answer but have working out is certainly possible to obtain marks.

In a subject where you hear numerous stories of people mistyping things into their calculators and obtaining an incorrect final answer, I really don't understand why you would simply write an answer and nothing else, especially considering it takes, what, an extra 5 seconds to write?  ???
I'm the type of person that will show working even if the questions is worth 1 mark, there's no way I'm ever gonna write an answer without the working shown. I was just curious about whether the examiners have concrete rules for allocating marks
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Jaswinder

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Re: VCE Physics Question Thread!
« Reply #224 on: October 12, 2013, 03:59:53 pm »
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1)what effect does changing the slit width have on the diffraction pattern?
2) What would be the range of answers expected for 2005 VCAA Exam 2 question 2 from Light and Matter Section
3) Are we expected to know about the mechanism by which light is produced in an incandescent light?
4) In a transformer, Joan increases the load on the secondary side of the transformer. Suddenly, it
stops working. She suspects that the fuse in the primary circuit has blown and intends to replace it.

In order to replace the fuse as safely as possible, which of the following is the best precaution for Joan to
take?
A. stand on a rubber mat
B. switch off the mains supply
C. disconnect the transformer from the mains supply
D. remove the load from the transformer

Why C instead or B?

Thanks