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HSC Physics Marathon 2013-2015 Archive (4 Viewers)

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Kaido

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re: HSC Physics Marathon Archive

How does doping affect the way a current is carried in a semiconductor? (5)
 

Crisium

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re: HSC Physics Marathon Archive

u have to use meisner affect and explain the balance between the weight force and the force of magnetic repulsion resulting from the interaction
of the fields of the induced current and hovering magnet.
It's also good to mention the exclusion of the magnetic field from the superconductor

@indolence I've heard explanations of the Meissner effect with Lenz's Law but for HSC physics I don't think they want you to relate the two

For your question I would've included the following:

When a superconductor is cooled below its critical temperature it will experience zero electrical resistance do to the formation of Cooper Pairs (as predicted by the BCS theory) and the Meissner effect in which the magnet fields are expelled from the superconductor forcing the magnet to hover/levitate. It will remain hovering/levitating in the same position despite being pushed around due to the quantum pinning phenomena. However, this effect wears off when the superconductor rises above its critical temperature.

Should probably mention the terms diamagnetic and paramagnet somewhere in there as well

I haven't looked at I2I section 4 in a while so someone correct me if I'm wrong
 

Physicklad

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re: HSC Physics Marathon Archive

I would say A more than B although A is not perfect.... non of these answers are right. The real graph should look very similar to B, but it must extend below the t axis for at least a infinitesimal period of time. How would you get a moving stone to stop moving unless you apply a counterbalancing force?

if the answer is B, picture this: the moving stone gets to the bottom and then acceleration drops to zero. so the stone continues with a constant velocity after hitting the ground......???? dont make sense m8

so the graph must certainly extend below the t axis - but not for as long as shown in A
 
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re: HSC Physics Marathon Archive

I would say A more than B although A is not perfect.... non of these answers are right. The real graph should look very similar to B, but it must extend below the t axis for at least a infinitesimal period of time. How would you get a moving stone to stop moving unless you apply a counterbalancing force?

if the answer is B, picture this: the moving stone gets to the bottom and then acceleration drops to zero. so the stone continues with a constant velocity after hitting the ground......???? dont make sense m8

so the graph must certainly extend below the t axis - but not for as long as shown in A
jelly
 

InteGrand

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re: HSC Physics Marathon Archive

I would say A more than B although A is not perfect.... non of these answers are right. The real graph should look very similar to B, but it must extend below the t axis for at least a infinitesimal period of time. How would you get a moving stone to stop moving unless you apply a counterbalancing force?

if the answer is B, picture this: the moving stone gets to the bottom and then acceleration drops to zero. so the stone continues with a constant velocity after hitting the ground......???? dont make sense m8

so the graph must certainly extend below the t axis - but not for as long as shown in A
Maybe the one in (B) actually went below the t-axis for a tiny amount, but too small for our eyes to see. :p
 

Crisium

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Maybe the one in (B) actually went below the t-axis for a tiny amount, but too small for our eyes to see. :p
InteGrand being racist wot (lel jks)

I think the graph is restricted to when it stops the moment the rock hits the water

+ InteGrand what's your (HSC level) understanding of the Meissner effect?
 

InteGrand

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InteGrand being racist wot (lel jks)

I think the graph is restricted to when it stops the moment the rock hits the water

+ InteGrand what's your (HSC level) understanding of the Meissner effect?
Impossible to understand at HSC level. I'd just memorise whatever the TB says for that (like Jacaranda).

For a true explanation, one must have a look at the London Equations: https://en.wikipedia.org/wiki/London_equations
 

Kaido

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re: HSC Physics Marathon Archive

What are the advantages of DC transmission over AC transmission (5 marks)
 

Crisium

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Since it's a discuss question, the only disadvantage I can think of at the moment is the technological and infrastructural costs required to cool and maintain the superconductors below critical temp.
The infrastructural cost will also include changing all power stations to DC since superconductors only work with DC (Cooper pairs cannot form under AC since the Cooper pairs only travel in one direction)

No transformers required to step up/down since little to no energy costs

Less coal is required to be burnt to produce the same amount of electricity thus further lowering the energy costs
 

Drsoccerball

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What are the advantages of DC transmission over AC transmission (5 marks)
Devices use DC and therefore no change is required from power station to device.

AC are affected by external magnetic fields (ceebs going into too much detail)

DC can use superconductors which allow for more efficient power transfer

DC doesn't lose energy like AC which uses it up in the form of eddy currents

Safer when closer to the user unlike AC which has 240V near the user

etc...
 

turnerloos

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re: HSC Physics Marathon Archive

are we allowed use 3u method to solve physics projectile quesitons?
 

malcolm21

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Use delta(x) = Ux*t in order to find t in terms of U

I don't get what this formula is?
 
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