Physics marathon (hsc) (8 Viewers)

[adzlark]

ridiculous question

I concur. Doesn't change the fact that they love putting this type of shit in the exams -_-

 

[dawooddaman]

Who's up for an all nighter?

 

[lemon1]

I know this sounds funny to ask.. But i never knew..

To determine the magnitude of the force between two parallel conductors, the formula is B = KI / d

Which formula's did they derive that formula from? I've messed around with k/d = kII/d and f = BIL sin theta but yeah, not working

also, heres a good question

Jenny is a 15 year old girl. Her 35 year old cousin, Andre, is an astronaut. Andre is t be launched into space for a non-stop, round trip journey into deep space that will take 25 years. Jenny finds the results unusual but calculates that in 25 years, when Andre returns to earth, both will be the same age, 40!

How fast would the space ship travel on this journey?

 

[RishBonjour]

Who's up for an all nighter?

staying up until I finish the content. don't think will get any past papers done.
Usual plan. sleep at 2. Wake up at 6. start studies. Go to school at 8.45
FKKKKKKKKKK CANT WAIT TO FINISH THIS SHIT

 

[LlamaBoi]

I know this sounds funny to ask.. But i never knew..

To determine the magnitude of the force between two parallel conductors, the formula is B = KI / d

Which formula's did they derive that formula from? I've messed around with k/d = kII/d and f = BIL sin theta but yeah, not working

also, heres a good question

Jenny is a 15 year old girl. Her 35 year old cousin, Andre, is an astronaut. Andre is t be launched into space for a non-stop, round trip journey into deep space that will take 25 years. Jenny finds the results unusual but calculates that in 25 years, when Andre returns to earth, both will be the same age, 40!

How fast would the space ship travel on this journey?

For the first part, to be honest I've never even seen B = kI/d but I managed to derive it (kinda)
You should recheck your formulas. It's F/l = kII/d and the other one is correct. After playing around with them I was able to change it into the one you said
F = lkI^2/d and F = BILsin()
BILsin() = lkI^2/d
B = lkI^2/dILsin()
B = kI/dsin()
but if you assume that () = 90, as in a maximum value then you have your equation

for the second part, its pretty much saying that 25 years occur on earth whilst only 5 years occur on the moving spaceship
25 = 5/sqrt(1-v^2/c^2)
1/5 = sqrt(1-v^2/c^2)
0.04 = 1-v^2/c^2
v^2/c^2 = 1-0.04
v^2 = (3x10^8)^2*0.96
v = 293938769.1 ms^-1
v = 0.98c
He would have to have been travelling at 0.98c

 

[someth1ng]

Sleep at 11, wake up at 7:45, go to school.

 

[freeeeee]

staying up until I finish the content. don't think will get any past papers done.
Usual plan. sleep at 2. Wake up at 6. start studies. Go to school at 8.45
FKKKKKKKKKK CANT WAIT TO FINISH THIS SHIT

LMAO u have exactly the same plan as me although ima get on to past papers, im up for all nighter, lets keep this thread alive to at least 2 =D

 

[freeeeee]

Sleep at 11, wake up at 7:45, go to school.

Sounds like your set =D, the rest factor will benefit you more then

 

[Kimyia]

Reposting my earlier post, can anyone help tell me if this is right - I'm still confused!
If you just have a magnet sitting on top of a superconductor (before its cooled before its critical temp) and you cool that superconductor below its critical temp, the magnetic will levitate because of the Meissner effect and the superconductor expelling all external magnetic fields such that it overcomes the weight force of the magnet and it levitates - nothing to do with induced currents?
But, if you have a superconductor cooled below its critical temp and you dropped a magnet from above the superconductor, then you'd induce 'perfect' eddy currents that repel the magnet's magnetic field (and is strong enough to overcome the weight of the magnet) such that it levitates???

 

[LlamaBoi]

^that is correct but you should also note that as the magnet is pushed up due to the meissner effect as the superconductor gets cooled, a change in flux occurs and a current gets induced in the superconductor which helps the magnet levitate even more

 

[kiinto]

Reposting my earlier post, can anyone help tell me if this is right - I'm still confused!
If you just have a magnet sitting on top of a superconductor (before its cooled before its critical temp) and you cool that superconductor below its critical temp, the magnetic will levitate because of the Meissner effect and the superconductor expelling all external magnetic fields such that it overcomes the weight force of the magnet and it levitates - nothing to do with induced currents?
But, if you have a superconductor cooled below its critical temp and you dropped a magnet from above the superconductor, then you'd induce 'perfect' eddy currents that repel the magnet's magnetic field (and is strong enough to overcome the weight of the magnet) such that it levitates???

Meisner effect is separate from eddy currents.

^that is correct but you should also note that as the magnet is pushed up due to the meissner effect as the superconductor gets cooled, a change in flux occurs and a current gets induced in the superconductor which helps the magnet levitate even more

No. The change in flux that occurs should in fact resist the change which caused it. Hence it should actually resist the magnet's levitation.

 

[freeeeee]

@Kim, superconducting properties will exist at any temperature at or below Tc- so for both circumstances Meissner effect will occur.
Not sure what you mean by perfect eddy currents

 

[someth1ng]

Reposting my earlier post, can anyone help tell me if this is right - I'm still confused!
If you just have a magnet sitting on top of a superconductor (before its cooled before its critical temp) and you cool that superconductor below its critical temp, the magnetic will levitate because of the Meissner effect and the superconductor expelling all external magnetic fields such that it overcomes the weight force of the magnet and it levitates - nothing to do with induced currents?
But, if you have a superconductor cooled below its critical temp and you dropped a magnet from above the superconductor, then you'd induce 'perfect' eddy currents that repel the magnet's magnetic field (and is strong enough to overcome the weight of the magnet) such that it levitates???

Yes, that is correct however you should say that the currents produce in the superconductor REPEL the magnet due the currents induced by the Meissner effect to oppose the magnetic flux. You should just say that a persistent eddy current is formed.

 

[someth1ng]

Meisner effect is separate from eddy currents.

In his case, it is an eddy current because when the magnet is dropped/moved near the superconductor, it experience a change of flux.

 

[LlamaBoi]

Oh wow you're right, the change in flux will actually drag the magnet down
Good catch haha

 

[kiinto]

Yes, that is correct however you should say that the currents produce in the superconductor REPEL the magnet due the currents induced by the Meissner effect to oppose the magnetic flux. You should just say that a persistent eddy current is formed.

Oh man. As far as I've seen you know your shit, so I'm inclined to trust what you're saying. Although, as far as I knew the Meissner Effect was separate, totally different thing, to induced magnetic fields.

"the fundamental origins of diamagnetism in superconductors and normal materials are very different."

- From wikipedia

Edit: I mean, eddy currents will be induced, however they do not have anything to do with the levitation, right?

 

[someth1ng]

Although, as far as I knew the Meissner Effect was separate, totally different thing, to induced magnetic fields.

Yeah, but superconductors can still experience a change of flux and hence, an induced emf. If you move a superconductor into a magnetic field, internally, it will have an eddy current induced. It still has no flux penetrating it due to the eddy current (still in line with Meissner effect) but the source of the current is slightly different.

I hope that makes some sense.

I mean, eddy currents will be induced, however they do not have anything to do with the levitation, right?

I believe it is at least related to levitation because it's a repulsion force...

 

[steero1]

Whoever answers this correctly deserves an award.
Identify differences in p-type and n-type semiconductors in terms of the relative number of negative charge carriers and positive holes.(4-marks)

 

[lolcakes52]

Whoever answers this correctly deserves an award.
Identify differences in p-type and n-type semiconductors in terms of the relative number of negative charge carriers and positive holes.(4-marks)

p-type has more holes and less negative charge carriers, n-type has less holes and more negative charge carriers.

 

[alexobern]

p-type, extra positive hole in valence band, n-type, extra electron in valence band...? i think