Want to compare multiple-choice answers? (1 Viewer)

[suchet_i]

the explanation u just gave means that the current flows from x to the globe to y .. thats C not b .. unless my paper had a typing problem in it

 

[typical_azn]

i thought this would happen, u must have impaired vision, if you read it, it says electron flow, which means conventional current flows in its opposite direction.

 

[gamecw]

i thought this would happen, u must have impaired vision, if you read it, it says electron flow, which means conventional current flows in its opposite direction.

lol?

 

[shinji]

yay. tht means there's a chance i'll get either 13-14/15!! =D

woot ! ^_^

 

[zeek]

The solution for question 10 is A for the the following reasons:

1) Initially when the switch is closed for a short time, a magnetic field is created extending into the secondary coil. As the field is not changing, then the only time an emf is induced in the secondary coil is when it first cuts the secondary coil. This emf is negative because Lenz's law states that an induced emf will produce a magnetic field that will oppose the original change in flux and the original emf is positive.

2) As the switch is held the emf does not change hence the magnetic field does not change and .: ΔΦ=0 resulting in an emf of zero, as represented by the graph.

3) At the final stage, the switch is released and the emf in the primary coil reduces to zero. As this reduction occurs, the magnetic field decreases in intensity and thus the flux cutting the secondary coil moves to the opposite direction. Again, by applying Lenz's law, the magnetic field created in the secondary coil is to oppose the change in flux thus the emf becomes positive.

 

[dartm2]

question 10 has many uncertainties, im not to sure either, it doesnt say wether its AC or DC,

Think Its dc, look at the power source diagram, it is the 2 dashs, meaning DC. AC power sources are shown as a circle with a sine wave in it.

 

[Benmc]

Wholly crap.
This threads totally undermined my confidence.

WTF...Why did i put C for the stupid Q2????? That'll haunt me forever.

But yes.
7 = D
8 = B (According to my teacher)....I put C....Why can flux be negative???? Shouldn't it be an absolute value curve???

9 = (No Fricking Idea) I put D tho.....No split ring, assumed it was D.
10 = A (According to my teacher) I put B i think, but yes..A is correct after looking at it.

So yeah...All the controbersial questions answered.
I think i got 9/15....LOL...thats really pathetic...Even less than my trials i think....

WTS

 

[mlinger]

does anyone have a copy of the mulitple choice they could post here???

 

[tojaco]

ummm for question 10.... it does the power supply is non alternating (ie DC)
it cant be d because they are inphase and transformers would have X at max when Y is at max
now if it is DC i think answer is A because initial circuit would have increase and then a plateau then drop off when it is turned off but because it is Dc the only change in the second winding would be when switch is turned on and off..... so i think a

 

[kobz]

this is wat i had down:

1) C
2) B
3) D
4) C
5) D
6) A
7) C
8) B
9) A
10) D
11) A
12) D
13) D
14) C
15) A

can any1 tell me my mark 4 this part????

 

[suchet_i]

u got 9/15
4-b
7-d
8-a
9-c
10-a
12-c

 

[HazamataX]

I think i got the answer to question 8 --- B

For proof go to the 2002 HSC....QS 10

Very similar and the answer is B

Keep in mind that induced emf is proportional to the rate of change of magnetic flux. Therefore the question is essentially the same

Look where the coil is perpendular to the field

From that...the answer is B

That's an unfortunate error u've made there. The answer is A. What you have confused is EMF (given by B) and the FLUX itself (given by A). Since the coil is PERPENDICULAR to the field intiially, the flux is a max. people who put C mustve seen a graph of the current in a DC generator and gone from there.

 

[bboyelement]

man im so confused with 9 ... but i put down C ... its over now who cares

 

[Rax]

Can people tell me what they put for 15 because everyone in my class said they had Aluminium and I had Barium I think, I put b anyway.

Need to find question sheet

 

[HazamataX]

AH FK FK FAAAAARRRRRRK! I fooled myself alright. Assholes planted answers for Q)7. THe noobs who had 7)B just plugged it all in = WRONG. You had to use pythagoras, which i did, but then u also had to realise that u dont plug in sin45 coz the B field is INTO the page so its always going to sin90. Argh (-1).

I can confidently say that Q8 is A. Its not about emf, or torque, as implied by B, and the reasoning that flux is a vector quantity and therefre cant be negative and hence it is C, is also WRONG (my teacher evne said it was fkn C). Question 9 is either B or C its contradicted everywhere. I put D but didnt even think of the diagram. (-2). And Q 10 is hands down A. I put D like many of u but its all about the 2ndary coil opposing changes, as shown by the downward trough when the field is applied, and the upwards peak when its pulled out...get it? The rest are synch. Q 15 needed u to know the formulas and get A. Im lookin at 12/15...is that alright?

 

[shinji]

yeh, ,i put b.
it's A [for question 10]

there is gonna be constnat current /voltage flowint through coil x when the switch is closed.

however, coil Y requires a change in flux to create a current [achieved by opening and closing the flux] and hence, voltage is induced in coil y

 

[bboyelement]

AH FK FK FAAAAARRRRRRK! I fooled myself alright. Assholes planted answers for Q)7. THe noobs who had 7)B just plugged it all in = WRONG. You had to use pythagoras, which i did, but then u also had to realise that u dont plug in sin45 coz the B field is INTO the page so its always going to sin90. Argh (-1).
QUOTE]


ahh fuk ... dammit ...ahh shit i did the same thing like you ... bastard

 

[jed.hamers]

Wanted to be smart and tell everyone they were wrong for #7. But as i read that had already been done. Answer is C = 0.6N. Have to use pythagorus theorum to find diagonal length, no just a simple sub in as everyone else is saying it's D. THE ANSWER FOR 7 IS C

 

[tojaco]

Wanted to be smart and tell everyone they were wrong for #7. But as i read that had already been done. Answer is C = 0.6N. Have to use pythagorus theorum to find diagonal length, no just a simple sub in as everyone else is saying it's D. THE ANSWER FOR 7 IS C

sorry dude i had C too but think about it.... u dont times it by sin 45 .... the angle is sin 90 because the field is perpendicular nayway.... yes u had to use pythagoras but it was sin 90

 

[jed.hamers]

sorry dude i had C too but think about it.... u dont times it by sin 45 .... the angle is sin 90 because the field is perpendicular nayway.... yes u had to use pythagoras but it was sin 90

awww piss. Damn.

Thanks for the explanation.