Exam 2 - good or bad?

[#1procrastinator]

Here's hoping for a low cut-off, really need a C+

[TheRajinator]

thought the first and second question were tricky. 1st question got south east, and second question I said the magnet remained the same as the question told us to ignore earth's magnetic field and the megnetic field at point Q was very weak hence the magnet satyed the same. what did everyone else get?

[Hutchoo]

The exam wasn't too bad. Sound was very, very straight forward! In fact.. all of the sound questions were pretty much identical to the VCAA papers. The exam in general was pretty long though. Just finished with like 3 seconds to go haha.

[#1procrastinator]

Science damn it, I didn't have time to go over the sound part of the past exams

[Hutchoo]

Science damn it, I didn't have time to go over the sound part of the past exams

I "did a rohit" - I learnt what Lenz's law and what a standing wave was ON the day of the exam..

In fact, if my friends didn't tell me that changing slip (SPLIT ? IDK LOL WHO GIVES A FK)  rings for a commutator results in pulse DC, I would have lost like 2 marks LOL.

DATCRAM
GETTING READY FOR UNI ALREADY

[vcestudent94]

fuck fuck fuck. I fucked up the whole transmission question, 5 marks definitely gone! I dont know what I was thinking, I went: I=V/R=900/18=50A but i know thats wrong fuck. Then I used that for the next 3 mark question. Please can anyone help me: If I used the wrong current of 50A in determining the Power loss in the next question, would I get ANY consequential marks? Please I need this answered Im dying!

You will lose one mark max, assuming you showed working for the other questions. Relax you will be fine.

Thank you for your kind words, however the way I  alculated the current was completely illogical since I just assumed that the motor would get 900V in th first place. I then went on to calculate the power loss which left the motor with less than the required power to use 9000V. Do you get what Im saying? But if I applied the rules correctly:Ploss=I^2R how many method marks am I looking at, 1 out o the total 3?

Anyone have any idea? thanks

[dazz95273]

For the question about two methods to reduce power loss...

First was obviously use a transformer.

But the second was confusing me. I was initially thinking to decrease the resistance by using thicker wires or a better conductor or electricity, but because I=V/R, if R decreases then I increases! And because PLoss=I^2R, any slight increase in I will be squared and actually increase the power loss by quite a bit.

So I eventually said to 'add more transmission wires in parallel', but that's effectively the same as decreasing R/increasing I, and at that point I gave up.


So which of the answers for the second method is correct (1: decrease R, or 2: add in parallel)? Are none correct, is one correct and the other isn't, or are both correct?

very confuzzled

hah...you should have went with thicker wires...cause the resistance is inversely proportional to cross-sectional area...but its ok...i thought that exam was a bit on the hard side...

[das3150]

i have a feeling there was a big trick question in there.
the question which showed the 2 magnets, and had like, A and B. it asked which direction the coil moved once the motor was swtiched on.
well anyway, the magnet had N and S on the top, and were shaded.
so..
the magnetic field wasnt going from North to south horizontally
it was going in an arch.

I thought the same, but dismissed the idea on the basis that it was a VCAA exam, not Itute lol. It could still be right, but it seems too damn ambiguous. The top half of the DC power supply was shaded too, so I really can't tell.

[pi]

Science damn it, I didn't have time to go over the sound part of the past exams

I "did a rohit" - I learnt what Lenz's law and what a standing wave was ON the day of the exam..

<3

[Charlatan]

Just to clarify:

Magnetic north does not refer to the "north pole" if you were to imagine earth as a bar magnet.

Magnetic north is the direction in which a compass needle says north is. This is different to "true north" which is towards the North pole (The geographical one in the Arctic). Going with the earth-is-a-bar-magnet idea, magnetic north can be equated to that magnet's south pole.

[damon2g]

Can someone tell me what Study Score a High C+ on exam 1 (~60/90) then A/A+ on Exam 2 is (~84/90)

[availn]

Just to clarify:

Magnetic north does not refer to the "north pole" if you were to imagine earth as a bar magnet.

Magnetic north is the direction in which a compass needle says north is. This is different to "true north" which is towards the North pole (The geographical one in the Arctic). Going with the earth-is-a-bar-magnet idea, magnetic north can be equated to that magnet's south pole.

Looking that up, holy crap, you're right. While I'm happy that I got that mark, this is some of the least intuitive crap I've ever seen...

[bubblefighter]

Shouldn't the first answer be North West. The field of the solenoid pointed west while the field of the Earth pointed north. Addition of vectors gives you North West. Or maybe I made a mistake in the exam room. All in all, good paper, some hard questions (I love you VCAA, made up for the easy methods one).

[tuffield2003]

Shouldn't the first answer be North West. The field of the solenoid pointed west while the field of the Earth pointed north. Addition of vectors gives you North West. Or maybe I made a mistake in the exam room. All in all, good paper, some hard questions (I love you VCAA, made up for the easy methods one).

Solenoid pointed east unfortunately!

[bubblefighter]

Shit :/, thought I nailed the crap out of that one. Oh well, still eludes me how I got part two correct though. 100% said C