Exam thoughts?? (1 Viewer)

kashkow

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Is this the one with the electron travelling in the magnetic field? I don't remember the exact number I got, but my direction was down the page.
Yeah I kept getting confused with this question with all the right hand rules and stuff... I think this was my method in the end:


x x x x

x x x x (e)--->

x x x x


this is the ELECTRIC field into the page and the electron. Rotating everything upwards you get

^ ^ ^ ^
| | | | (e)--->
| | | |
| | | |

Electron will travel downwards therefore you need a magnetic field that is out of the page for balance.

. . . . . . .

. . . . . . .

. . . . . . .

Rotating everything back makes it go up the page. That's just my thinking anyway - could be wrong. (I can't remember if I rotated it this EXACT way in the test but I used the same method of rotating the fields around).

Anyway, that's if you still care :p
 

MeepTMW

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Could you explain this please? You're probably right but I thought that a north pole would be created at the right to attract to the south and reduce motion (Lenz's Law), causing anitclockwise current by right hand grip rule so would go X to Y?
I looked at the upper part of the solenoid from top-down and found that the currents going in were pointing into the page (Since the magnetic field was downwards, and the force leftward). Hence the current in the solenoid looking from the direction of the loudspeaker was clockwise so it was Y->X. I considered Lenz's Law as well, but dismissed as thinking too hard. I do understand your thinking though and am inclined to believe yours more. So your answer, A, is more likely.
 

baktiar77

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I wish that rope in q30 was around my neck. Can't believe how many multiple choice questions I fucked up and I left out q30 cause i ran out of time. And it wasn't even that hard of an exam, i just spent way too long on some questions and I'll endup losing a mark here and there. FML.
 

kashkow

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Ah I got the same direction but magnitude got like 1.9 x10^-4 tesla
that's probably right. I can't remember the exact figure but could probably quickly work it out again now...


basically what I did was (that is after a while - was using wrong formula to begin with then left the question and came back in the end):

qvB=Eq



vB=10

B=10/v and I think v was like 5.4*10^4 or something

= 1.85185... e-4

So I probably got that as well :) Unless I did something silly in my writing because I rushed :S
 

jazz519

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that's probably right. I can't remember the exact figure but could probably quickly work it out again now...


basically what I did was (that is after a while - was using wrong formula to begin with then left the question and came back in the end):

qvB=Eq



vB=10

B=10/v and I think v was like 5.4*10^4 or something

= 1.85185... e-4

So I probably got that as well :) Unless I did something silly in my writing because I rushed :S
Yep did that as well :)
 

mrstripedshades

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Im pretty confident for most of the non maths based questions, think I made silly mistakes here and there for the maths ones. And I already knew I fked multi choice LOL (my trials one was even worse), but I think I can get a mid 70's raw. This was my spare subject tho so w/e XD
 

henryg124

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EDIT: Request for somebody, can somebody please tell me what they got for Q17 MCQ? I chose C as the answer (trajectory is slightly above original trajectory). This was the elevator question.
I just thought about what it feels like when youre in a car and you go over a hill, you feel that weightless feeling. Same thing when an elevator comes to the top. the acceleration due to gravity seems to get smaller, and so it hangs in the air for longer. i got C
 
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