HSC Physics Marathon 2013-2015 Archive (2 Viewers)

Status
Not open for further replies.
Fizzy_Cyst

Fizzy_Cyst

Well-Known Member
Joined
Jan 14, 2011
Messages
1,189
Location
Parramatta, NSW
Gender
Male
HSC
2001
Uni Grad
2005
re: HSC Physics Marathon Archive

someth1ng said:
In reality, they are produced but in HSC, you say they are not produced.
Click to expand...
#hscsez

As above. As soon as there is a slit, there is no loop for the eddy currents to flow around in.

This is one of the scenarios where if you know too much (I.e., what REALLY happens) you will get it wrong.
 
Last edited:
Kaido

Kaido

be.
Joined
Jul 7, 2014
Messages
823
Gender
Male
HSC
2015
re: HSC Physics Marathon Archive

Fizzy_Cyst said:
#hscsez

As above. As soon as there is a slit, there is no loop for the eddy currents to flow around in.

This is one of the scenarios where if you know too much (I.e., what REALLY happens) you will get it wrong.
Click to expand...
seems legit
 
Kaido

Kaido

be.
Joined
Jul 7, 2014
Messages
823
Gender
Male
HSC
2015
re: HSC Physics Marathon Archive

Any other 'scenarios' regarding the HSC exams?
 
D

Drsoccerball

Well-Known Member
Joined
May 28, 2014
Messages
3,657
Gender
Undisclosed
HSC
2015
re: HSC Physics Marathon Archive

Just finished generators. Stupid question though. If i kept turning my charger on and off would it charge faster as there is little back emf?
 
anomalousdecay

anomalousdecay

Premium Member
Joined
Jan 26, 2013
Messages
5,769
Gender
Male
HSC
2013
re: HSC Physics Marathon Archive

Drsoccerball said:
Just finished generators. Stupid question though. If i kept turning my charger on and off would it charge faster as there is little back emf?
Click to expand...
No. Mains supply is 240 V 50 Hz AC. Also, the charger will behave as two inductors for a transformer setup. The secondary end will be it's own circuit. AC analysis is something completely out of the scope of HSC level work, but the inductor will have a relative impedance and hence a phasor voltage and phasor current which will be dependent of the AC voltage input.

Good question, but requires a more in depth analysis of what is going on.
 
D

Drsoccerball

Well-Known Member
Joined
May 28, 2014
Messages
3,657
Gender
Undisclosed
HSC
2015
re: HSC Physics Marathon Archive

Explain how changing understanding of Len's Law and Eddy current has led to the development of new technologies which can benefit society. 7 Marks
 
Kaido

Kaido

be.
Joined
Jul 7, 2014
Messages
823
Gender
Male
HSC
2015
re: HSC Physics Marathon Archive

- lenz's law states that an emf induced as a consequence of faraday's law will induced a current in such a direction that the mag. field it produces opposes the motion of the mag. flux that produced it -> production of back eddy currents...
- prev. conceived as an inefficient energy transformation due to the formation of eddy currents that oppose the supplied emf/current -> thus transformers (as an ex.) are unable to ideally transform 100% of the energy input + power transmission energy loss -> costing society both money, resources and production supply -> environmental effects etc.

would this be a part of the marking crit?
 
D

Drsoccerball

Well-Known Member
Joined
May 28, 2014
Messages
3,657
Gender
Undisclosed
HSC
2015
re: HSC Physics Marathon Archive

Kaido said:
- lenz's law states that an emf induced as a consequence of faraday's law will induced a current in such a direction that the mag. field it produces opposes the motion of the mag. flux that produced it -> production of back eddy currents...
- prev. conceived as an inefficient energy transformation due to the formation of eddy currents that oppose the supplied emf/current -> thus transformers (as an ex.) are unable to ideally transform 100% of the energy input + power transmission energy loss -> costing society both money, resources and production supply -> environmental effects etc.

would this be a part of the marking crit?
Click to expand...
wouldnt get full marks..you have to speak about specific technologys like induction cook tops, electromagnetic brakes ect..
2 marks goes to defining lens law and eddy currents. you didnt define new technologys but stated the problems with the old ones
 
Kaido

Kaido

be.
Joined
Jul 7, 2014
Messages
823
Gender
Male
HSC
2015
re: HSC Physics Marathon Archive

ahh yeah, i just wanted to know whether it satisfied the first half of the question, haha :D
 
D

Drsoccerball

Well-Known Member
Joined
May 28, 2014
Messages
3,657
Gender
Undisclosed
HSC
2015
re: HSC Physics Marathon Archive

Really good question to test understanding.
"The slingshot effect can increase the speed of a spacecraft""
Explain how this can be true in some frames of reference but not in others.
 
I

InteGrand

Well-Known Member
Joined
Dec 11, 2014
Messages
6,109
Gender
Male
HSC
N/A
re: HSC Physics Marathon Archive

Drsoccerball said:
Explain how changing understanding of Len's Law and Eddy current has led to the development of new technologies which can benefit society. 7 Marks
Click to expand...
By the way, it's spelt Lenz's Law (the guy's name was Lenz). (Just saying in case the markers are pedantic and take off marks if you write 'Len's' instead of 'Lenz's'.)
 
Kaido

Kaido

be.
Joined
Jul 7, 2014
Messages
823
Gender
Male
HSC
2015
re: HSC Physics Marathon Archive

Drsoccerball said:
Really good question to test understanding.
"The slingshot effect can increase the speed of a spacecraft""
Explain how this can be true in some frames of reference but not in others.
Click to expand...
- gravitational field of a planet 'pulls' a spacecraft in -> accelerating as it comes in and decelerating as it leaves relative to the planet
- as the planet rotates about the sun, its angular momentum is transferred to the spacecraft giving it a velocity boost relative to the sun
 
D

Drsoccerball

Well-Known Member
Joined
May 28, 2014
Messages
3,657
Gender
Undisclosed
HSC
2015
re: HSC Physics Marathon Archive

Kaido said:
- gravitational field of a planet 'pulls' a spacecraft in -> accelerating as it comes in and decelerating as it leaves relative to the planet
- as the planet rotates about the sun, its angular momentum is transferred to the spacecraft giving it a velocity boost relative to the sun
Click to expand...
The acceleration of the planet is greater than the deceleration of the planet when leaving. The answer is :
According to the planet there is no change in velocity while in the frame of reference of the sun the spaceship gained speed.
If youre on a planet and you see a spaceship use the slingshot effect there would be no change in speed from your perspective:)
 
Kaido

Kaido

be.
Joined
Jul 7, 2014
Messages
823
Gender
Male
HSC
2015
re: HSC Physics Marathon Archive

Drsoccerball said:
The acceleration of the planet is greater than the deceleration of the planet when leaving. The answer is :
According to the planet there is no change in velocity while in the frame of reference of the sun the spaceship gained speed.
If youre on a planet and you see a spaceship use the slingshot effect there would be no change in speed from your perspective:)
Click to expand...
I remember there was something "relative to the planet" as well :O
 
P

PhysicsMaths

Active Member
Joined
Dec 9, 2014
Messages
179
Gender
Male
HSC
2015
re: HSC Physics Marathon Archive

Assess the impacts of A.C. generators on society and the environment
 
Status
Not open for further replies.

Users Who Are Viewing This Thread (Users: 0, Guests: 2)

Top