HSC Physics Question Thread

[Bubbly_bluey]

Oops my bad I thought the right one was positive for some reason!

As stated before, the reason why isn't in the HSC course. It has to do with the fact that the input voltage is DC which is why the formula np/ns = Is/Ip does not work. It's dumb that BOSTES put that question in.

If it was an AC input the answer should be what you said.

whaat itsnot in the syllabus >: ( How did you know it was DC?

[blasonduo]

whaat itsnot in the syllabus >: ( How did you know it was DC?

The battery pack indicates this DC pack. I'm curious though, because if we were to change the voltage to AC, would it change the answer?

[pikachu975]

whaat itsnot in the syllabus >: ( How did you know it was DC?

I knew cause I read online that it's a bad question because we don't use DC transformers in HSC plus the input isn't AC.

The battery pack indicates this DC pack. I'm curious though, because if we were to change the voltage to AC, would it change the answer?

Yeah it'd be different

[winstondarmawan]

As stated before, the reason why isn't in the HSC course. It has to do with the fact that the input voltage is DC which is why the formula np/ns = Is/Ip does not work. It's dumb that BOSTES put that question in.

If it was an AC input the answer should be what you said.

Actually, it does work even if it is only for a little while. Because there is a change in flux as soon as the switch is closed.

Anyways, if anyone could give a quick rundown on the scientists and their contributions to the Manhattan Project for Quanta to Quarks that would be SWEETTT. I'm having trouble finding the exact scientists which contributed both directly and indirectly.
TIA.

[pikachu975]

Actually, it does work even if it is only for a little while. Because there is a change in flux as soon as the switch is closed.

Anyways, if anyone could give a quick rundown on the scientists and their contributions to the Manhattan Project for Quanta to Quarks that would be SWEETTT. I'm having trouble finding the exact scientists which contributed both directly and indirectly.
TIA.

However we don't learn the specifics of how number of coils affects the output etc like we do for AC.

A quick one would be Einstein who suggested to start the project.

[jaskirat]

Ahhh but the thing with q20 is isnt the photons energy meant to exceed the band gap of the semiconductor in order to emit an electron?

Hey! So q14 is converting the magnetic flux graph to emf. (My explanation is using maths so I'm sorry if it doesn't make sense but I'll try) These two are linked together with the E= -change flux/ change time so like a differentiation q (you have to differentiate magnetic flux to get emf. Solooking at the magnetic flux graph at the origin is a point of inflection (POI) with positive graident, meaning on the emf graph should start above the x axis. BUT, remember the formula has a negative sign so its the opposite and actually starts at the bottom. Leaving options C and D. However when differentiating a POI you get a stat point so it should be D.
To confirm you can look back at the magnetic flux graph at the next time and you have a stationary point, gradient =0. Therefore that is an indication that you should have an x-int next.
q16 Im a bit iffy on back emf. But i think maybe because has the DC motor gain speed until it reaches constant velocity when back emf=supply emf. So there would not be any extra work/ no net force done because the induced emf would balance with the supply emf?? dont quote me on this but hence why I would pick C?
q20 I would find the energy of the photon at the peakof the graph so maybe around 8-9micrometres in wavelength. Use E=hf to find that energy. Then convert it to eV by dividing it by (1.602x10^-19). So I worked that out to be 0.155 eV which is how much you need. So 0.17eV would be enough to provide this.
Hope this help

[winstondarmawan]

Quanta to Quarks
Also, in discussing the positive and negative impacts of the Manhattan Project to society, I have been told that stating 'Potentially saving the lives of many Ally soldiers' was not a good positive impact to put as it is quite controversial.
Thoughts?

[statues]

oml lol sorry yeah galvanometers measure current. But the maths would still work in this case you would use Np/Ns=Is/Ip. rearrange to make Is subject. Is=(Np x Ip) / Ns. So yes it would be B. Sorry that was a really bad mistake XD. Hope this clears it up

Hey thanks so much for the help. I totally agree with your work but the HSC answer is A. So I'm still a bit confused. If the questions just wrong was it omitted from the hsc?

[statues]

Quanta to Quarks
Also, in discussing the positive and negative impacts of the Manhattan Project to society, I have been told that stating 'Potentially saving the lives of many Ally soldiers' was not a good positive impact to put as it is quite controversial.
Thoughts?

I would tend to agree with that assessment - don't say that. There's loads of positive impacts of the manhattan project such as the development of nuclear power, radioisotopes , understanding of quantum physics , the end of ww2 etc. It's just not necessary to make that point - while it's potentially true it seems to undermine the slaughter of 80000 Japanese civilians - which is a negative point you should discuss too. Having both points would seem to form to some degree an incongruous argument.  There's really nothing to be gained using this point-  there are no doubt HSC markers who are going to be offended - like imagine if you got some Japanese dude marking your question, it's not going to go well for you.
Anyways best of luck I'm doing the same option!

[winstondarmawan]

Hello! Would appreciate help with these MCs:
6. https://scontent-syd2-1.xx.fbcdn.net/v/t35.0-12/22883926_1362403753885144_473053551_o.jpg?oh=51a20dd5d7c37a1fa4e92f54e4601332&oe=59F5ABED
9. https://scontent-syd2-1.xx.fbcdn.net/v/t35.0-12/22883814_1362403813885138_1145465314_o.jpg?oh=2fb169176f21fc70c3a7d1ddc8aa51d3&oe=59F581D8
Thought the answer would be B, but the excel book has put the answer as C.
TIA.

[CyberScopes]

Hey thanks so much for the help. I totally agree with your work but the HSC answer is A. So I'm still a bit confused. If the questions just wrong was it omitted from the hsc?

Heres how I think of it:

We know Vp/Vs = np/ns
We also know that C and D are obviously wrong.
So we're left with A and B.
Both options assume Vp is constant, so set Vp to 1 for ease of calculation.
Since we're trying to maximise Vs for maximum deflection (Remembering that V = IR so more V means more current for deflection), we flip both sides so it becomes:
Vs/1 = ns/np
So Vs = ns/np

Now from this we can either increase ns, or decrease np to increase Vs.
Since increasing ns is not an option, u can only decrease np to increase Vs

Therefore answer is A

[jamonwindeyer]

Hello! Would appreciate help with these MCs:
6. https://scontent-syd2-1.xx.fbcdn.net/v/t35.0-12/22883926_1362403753885144_473053551_o.jpg?oh=51a20dd5d7c37a1fa4e92f54e4601332&oe=59F5ABED

Hey! For your first one, a current is produced in the wire due to its motion relative to the earths magnetic field. Note that the wire has very low resistance. So, going through the options:

- The orientation of the wire makes a huge difference - It needs to cut through magnetic field lines for an induced current to flow. So D is out.
- The speed of rotation affects the rate of change of magnetic flux, so C is out.
- The length of the wire also affects the size of the induced current (think of it like the longer wire being able to cut through more flux lines). So A is out.

The answer is B - The wire has a very low resistance so increasing its thickness won't do much at all

9. https://scontent-syd2-1.xx.fbcdn.net/v/t35.0-12/22883814_1362403813885138_1145465314_o.jpg?oh=2fb169176f21fc70c3a7d1ddc8aa51d3&oe=59F581D8
Thought the answer would be B, but the excel book has put the answer as C.
TIA.

The Excel book has simplified the scenario a tad - I know what you are thinking, but the eddy currents in both P and R are both negligible. P is an insulator so they don't flow, and the break in R has the same effect. So assuming both are negligible, they'll hit the bottom at the same time and then Q will follow

[jamonwindeyer]

Hey all! Just wanted to say I absolutely LOVE the awesome little community that has formed in this thread. Great to see everyone helping each other out in the lead up to the exam - You are all awesome!

If any questions got missed or we were stuck anywhere, repost/quote it below and I'll lend a hand if I can!! I've just finished submitting three assignments in 24 hours so I might not be much use at all, but hey, keen to do what I can to help you guys smash it out of the park on Monday 

[Dante1091]

Hello guys,

Are we allowed to use an ampersand (&), in replacement of 'and' in science tests. Since I know we aren't allowed to use it in subjects like English, but I'm unsure about the sciences.

[jamonwindeyer]

Hello guys,

Are we allowed to use an ampersand (&), in replacement of 'and' in science tests. Since I know we aren't allowed to use it in subjects like English, but I'm unsure about the sciences.

Absolutely - It probably would have been fine in English too but definitely fine here