Physics Exam 2 (End of Year) thoughts

[tolybangn]

can someone who has the exam please type up the verbatim instruction of the Faraday/Lenz law question??

Im almost certain that as I was reading it I knew that neither answer was a full explanation, and that both answers fit in accordance with the question (I believe it was along the lines of "what law was used to arrive at this graph" or something).

They really need to give the mark for either, in my opinion; the only way they could justify that one answer was correct is by using the "we are the VCAA and our interpretation is the only interpretation" argument.

(unrelated, but SERIOUSLY, last question of the GAT, asking us what ART OBJECTIVELY CONVEYS. They must think they are God or something.)

[Blakhitman]

What?.. Why does the equation not align with the explanation.. No matter.. Argh, I trusted the MGS guy at VU. He said Lenz's law is Faraday's with the negative >.<

I reckon a bastard examiner won't see what I meant and would penalise me for what he perceives as hedging my bets xD

MGS guy?

Um Geoff Davies ran the free VU lecture.

lol he ran the TSFX mid-year...got dropped ey  :buck2:

NO I'M OBVIOUSLY KIDDING derrrrr

[m@tty]

He does both. He said that he got paid much less for the VU one, but he does it because he likes to help students. He even said that he gave us, the attendees of the free lecture, more material than those who went to TSFX :buck2: Admittedly, this exclusive material was mostly preworked formulas, with things such as e, h, etc substituted.. Not that useful.. but still

[Whatlol]

can someone who has the exam please type up the verbatim instruction of the Faraday/Lenz law question??

Im almost certain that as I was reading it I knew that neither answer was a full explanation, and that both answers fit in accordance with the question (I believe it was along the lines of "what law was used to arrive at this graph" or something).

They really need to give the mark for either, in my opinion; the only way they could justify that one answer was correct is by using the "we are the VCAA and our interpretation is the only interpretation" argument.

(unrelated, but SERIOUSLY, last question of the GAT, asking us what ART OBJECTIVELY CONVEYS. They must think they are God or something.)

Identify the physical law you used for constructing your graph

[a.zirek]

it's gotta be lenz's law. negative gradient of flux change

Ermm... Negative gradient of flux change is Faraday's Law.

Lenz's law is about induced current

[kakar0t]

it's gotta be lenz's law. negative gradient of flux change

Ermm... Negative gradient of flux change is Faraday's Law.

Lenz's law is about induced current

I thought the physical law was the law of electromagnetic induction... but i put down faradays

[m@tty]

It's my understanding that the negative was not in the emf formula until Lenz put it there. Geoff Davies, the MGS guy that I was talking about earlier, said that Lenz made a link between LeChatelier's principle and the induced current - he reasoned that systems oppose change.. So the direction of the induced current must be such that it opposes the change. Davies said he chucked a negative sign out front of Faraday's emf formula, and it then became Lenz's law, rather than Faraday's...

Anyway, the point I'm getting at is that this guy said that with the negative it's Lenz's and without it it's Faraday's..

[a.zirek]

2005 VCAA Exam Question 15 asks:

'Compare and contrast Faraday's law and Lenz's Law.'

The answer:

'Faraday's Law gives the magnitude of the induced current, while Lenz's law gives the direction.'

[Xavier1234]

It's my understanding that the negative was not in the emf formula until Lenz put it there. Geoff Davies, the MGS guy that I was talking about earlier, said that Lenz made a link between LeChatelier's principle and the induced current - he reasoned that systems oppose change.. So the direction of the induced current must be such that it opposes the change. Davies said he chucked a negative sign out front of Faraday's emf formula, and it then became Lenz's law, rather than Faraday's...

Anyway, the point I'm getting at is that this guy said that with the negative it's Lenz's and without it it's Faraday's..

geoff davies? he's my teacher. lolz

[Xavier1234]

It's my understanding that the negative was not in the emf formula until Lenz put it there. Geoff Davies, the MGS guy that I was talking about earlier, said that Lenz made a link between LeChatelier's principle and the induced current - he reasoned that systems oppose change.. So the direction of the induced current must be such that it opposes the change. Davies said he chucked a negative sign out front of Faraday's emf formula, and it then became Lenz's law, rather than Faraday's...

Anyway, the point I'm getting at is that this guy said that with the negative it's Lenz's and without it it's Faraday's..

yeah he always bags lenz guy for apparently "just putting a negative sign" in faraday's eq. and end up winning a nobel prize himself. i dont remember him saying that faraday and lenz are the same though

[minimum]

What?.. Why does the equation not align with the explanation.. No matter.. Argh, I trusted the MGS guy at VU. He said Lenz's law is Faraday's with the negative >.<

I reckon a bastard examiner won't see what I meant and would penalise me for what he perceives as hedging my bets xD

MGS guy?

Um Geoff Davies ran the free VU lecture.

lol he ran the TSFX mid-year...got dropped ey  :buck2:

NO I'M OBVIOUSLY KIDDING derrrrr

He took the end of the year Sound too ( if i remember right)

[Xavier1234]

What?.. Why does the equation not align with the explanation.. No matter.. Argh, I trusted the MGS guy at VU. He said Lenz's law is Faraday's with the negative >.<

I reckon a bastard examiner won't see what I meant and would penalise me for what he perceives as hedging my bets xD

MGS guy?

Um Geoff Davies ran the free VU lecture.

lol he ran the TSFX mid-year...got dropped ey  :buck2:

NO I'M OBVIOUSLY KIDDING derrrrr

He took the end of the year Sound too ( if i remember right)

nah it was anthony novak. the guy who always delivered a 15minute hate speech against vcaa before lectures. wouldnt blame him one bit.

[tolybangn]

can someone who has the exam please type up the verbatim instruction of the Faraday/Lenz law question??

...

Identify the physical law you used for constructing your graph

Thanks; I think it proves my point.

I used both laws to construct my graph; I used Faraday's law to know the voltage was proportional to the change in flux, and I used Lenz's law to know that the line segments from 0 to 1 and from 2 to 4 (iirc) must be on opposite sides of the x axis (ie. one -ve, one +ve). Without both I could not have constructed my graph correctly.

The VCAA would be completely ignorant to even begin to argue that one answer is wrong.

[theuncle]

You guys are saying the circuit was in series?
I thought it was in parallel, as this halves the effective resistance and hence gives a power of 600W which was half of the original 1200W element.

[Whatlol]

You guys are saying the circuit was in series?
I thought it was in parallel, as this halves the effective resistance and hence gives a power of 600W which was half of the original 1200W element.

yea had to be in series. P = V^2/R
P = 240^2 / 96 = 600W