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March 29, 2024, 03:36:49 pm

Author Topic: VCE Physics Question Thread!  (Read 603446 times)  Share 

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Jaswinder

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Re: VCE Physics Question Thread!
« Reply #285 on: October 25, 2013, 07:26:23 pm »
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also just to be 100% sure, we can take in 2 double sided a4 sheets into the exam yeh? :)

BasicAcid

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Re: VCE Physics Question Thread!
« Reply #286 on: October 25, 2013, 08:05:13 pm »
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also just to be 100% sure, we can take in 2 double sided a4 sheets into the exam yeh? :)

They need to be stuck together, but yes.

Jaswinder

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Re: VCE Physics Question Thread!
« Reply #287 on: October 25, 2013, 08:31:35 pm »
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stuck together? how do i do that? you can't bound 2 A4 sheets can you? would stapling them together work?

Alwin

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Re: VCE Physics Question Thread!
« Reply #288 on: October 25, 2013, 08:34:46 pm »
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stuck together? how do i do that? you can't bound 2 A4 sheets can you? would stapling them together work?

you can try photocopying double sided onto A3 if you want :)
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Jaswinder

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Re: VCE Physics Question Thread!
« Reply #289 on: October 25, 2013, 08:38:40 pm »
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thatd be the last option  :( what else can we do?

Robert123

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Re: VCE Physics Question Thread!
« Reply #290 on: October 29, 2013, 08:18:43 pm »
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Having difficulty with this lenzs law from VCAA 2007 exam 2 Q14 & 15
Their reasoning for their answer is...
"when the switch was closed a magnetic field built up to the left. To oppose this, the induced current must produce a magnetic field to the left."
Wouldn't the induced current produce a field to the right?

angus_grant

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Re: VCE Physics Question Thread!
« Reply #291 on: October 30, 2013, 05:35:15 pm »
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"when the switch was closed a magnetic field built up to the left. To oppose this, the induced current must produce a magnetic field to the left."


Yeah must have been a typo, without looking at the question id say the flux increased in the left direction, and so to oppose this, a current was induced that had a flux in the right direction, then do the right hand rule to find current flow (guessing its a solenoid question or something similar)
hope this helps :)
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Robert123

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Re: VCE Physics Question Thread!
« Reply #292 on: October 30, 2013, 07:23:23 pm »
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Yeah must have been a typo, without looking at the question id say the flux increased in the left direction, and so to oppose this, a current was induced that had a flux in the right direction, then do the right hand rule to find current flow (guessing its a solenoid question or something similar)
hope this helps :)

I'm not sure if it was a typo, since it was a MC choice question, the answer would be the complete opposite. IF it is not too much of a hassle could be please have a look at it at http://www.vcaa.vic.edu.au/Documents/exams/physics/2007physics2.pdf page 11.

SocialRhubarb

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Re: VCE Physics Question Thread!
« Reply #293 on: October 30, 2013, 07:30:32 pm »
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Highly doubt there would be an error in VCAA solutions. If something's wrong they will revise it.

Okay, so when the switch is closed, the current is increasing, creating an increasing magnetic field. The field's direction points towards the left. At the second coil, the direction of the magnetic field is also pointing towards the left. The current induced in the coil will be such that it opposes the change, hence we want to induce a field towards the right. Creating a field  pointing towards the right requires a current to flow from Y to X.

The current only flows momentarily, as once the current maintains a steady value there will no longer be any change in flux and hence no induced current.

So the answer is B.
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Robert123

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Re: VCE Physics Question Thread!
« Reply #294 on: October 30, 2013, 07:43:16 pm »
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Highly doubt there would be an error in VCAA solutions. If something's wrong they will revise it.

Okay, so when the switch is closed, the current is increasing, creating an increasing magnetic field. The field's direction points towards the left. At the second coil, the direction of the magnetic field is also pointing towards the left. The current induced in the coil will be such that it opposes the change, hence we want to induce a field towards the right. Creating a field  pointing towards the right requires a current to flow from Y to X.

The current only flows momentarily, as once the current maintains a steady value there will no longer be any change in flux and hence no induced current.

So the answer is B.

But wouldn't a current flowing from Y to X produce a magnetic field to the left inside the solenoid? Using the RH grip rule on the leftest loop, your fingers would wrap around pointing to the left on the solenoid side

lzxnl

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Re: VCE Physics Question Thread!
« Reply #295 on: October 30, 2013, 07:54:50 pm »
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Close switch=>magnetic field to left induced=>increasing magnetic flux to left=>induced magnetic field to right=>use right hand rule, current goes from X to Y. OUTSIDE the ammeter. Through the ammeter, the direction is from Y to X.

The answer B is perfectly fine.
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Alwin

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Re: VCE Physics Question Thread!
« Reply #296 on: October 30, 2013, 08:14:06 pm »
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Alternate way of thinking:

 > Close switch
 > Magnetic field increasing to the left
    ^ using right hand grip rule
 > Same as moving towards a south pole
 > So south pole induced at the end closest to first coil
    ^ using Lenz's law
 > Current flows from Y to X
    ^ using right hand grip rule again

This alternate method works best when there is on magnet and coil moving towards each other / in circles / whatever vcaa wants lol
2012:  Methods [48] Physics [49]
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Jaswinder

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Re: VCE Physics Question Thread!
« Reply #297 on: October 30, 2013, 08:55:20 pm »
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whats a good cheatsheet appropriate definition for modulation and demodulation? thanks :D

Stevensmay

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Re: VCE Physics Question Thread!
« Reply #298 on: October 30, 2013, 09:40:07 pm »
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Modulation: Imprinting a lower frequency data signal onto a higher frequency carrier wave.
http://tele-information.com/wp-content/uploads/2012/10/Amplitude-modulation-AM.gif

Demodulation is the removal of the carrier wave to leave only the data wave. Reverse the above image.

Jaswinder

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Re: VCE Physics Question Thread!
« Reply #299 on: October 30, 2013, 10:24:31 pm »
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thanks man!

also this one, i get q to p but answers say p to q