Exam thoughts?? (2 Viewers)

[severus snake]

Personally i foudn it really hard

Hoping for at least 45 raw

 

[DatAtarLyfe]

Lmao at the MRI 6 marker in medical

 

[turntaker]

Hoping for 15 raw

 

[hedgehog_7]

Found it easier than last years? :l Hoping for a 87 raw

 

[henryg124]

Seemed a bit easier than past papers imho

 

[mrstripedshades]

Found it really easy tbh especially in comparison to my trials. Most trouble I had with was mc probably and kinda bullshitted some of Astro

 

[thomasdo1]

it was good, hoping for 90-95 raw

 

[porcupinetree]

Anyone have a copy of the paper? I wanna see it

 

[DatAtarLyfe]

It definitely was one of the easiest papers in the last couple of years.
I expect the cut off will be ~85-87

 

[cookie_dough]

what did people right about the velocity/time graph for the magnet and the metal?

 

[Ambility]

I think it was a pretty easy exam. I finished with plenty of time to spare. Here's a couple questions for everyone:

What did everyone use for their three discoveries including the electric generator?
Did anyone else freak out when they saw eV and didn't know what it was?
For the solar panel multiple choice question, does light create electron hole pairs or a pd between the PN junction?
For the last multiple choice question, with a DC motor connected to an AC power supply, does it vibrate to the frequency of the AC or does it alternate a half turn backwards and forwards?
For the makeshift light source of Mars, what happens when the switch is open?

Cheers.

 

[henryg124]

^ for the last MC
I thought it only turned clockwise because the AC turns the magnets into electromagnets which changes the electromagnetic field constantly, turning the coil constantly

 

[cookie_dough]

1. I wrote about semiconductors and superconductors
2. Nope
3. I am under the impression it was electron-hole pairs
4. I thought it alternated half turn forwards then half turn backwards
5. I said that mass will fall faster when switch is open. I thought that the induced emf generates a current opposing the change in flux (Lenz's Law) and therefore slowing the rotation when the switch is closed, cos current is allowed to flow. BUT I was not sure

 

[cookie_dough]

^ for the last MC
I thought it only turned clockwise because the AC turns the magnets into electromagnets which changes the electromagnetic field constantly, turning the coil constantly

crap ur right

 

[RachelGreen]

1. I wrote about semiconductors and superconductors
2. Nope
3. I am under the impression it was electron-hole pairs
4. I thought it alternated half turn forwards then half turn backwards
5. I said that mass will fall faster when switch is open. I thought that the induced emf generates a current opposing the change in flux (Lenz's Law) and therefore slowing the rotation when the switch is closed, cos current is allowed to flow. BUT I was not sure

I feel like it would be incorrect to talk about Lenz law for 5. I just said that due to law of conservation of energy, the rotor coils would be harder to turn (rotational kinetic energy) would decrease as the mass falls faster, thus mass falls experiences opositional force compared to when switch it open

 

[RachelGreen]

For the last question in core topics, regarding Mars and energy supplies to light bulb. Did anyone get 7.48 joules??? Or am I wrong

 

[thomasdo1]

^ for the last MC
I thought it only turned clockwise because the AC turns the magnets into electromagnets which changes the electromagnetic field constantly, turning the coil constantly

split-ring tho

 

[thomasdo1]

For the last question in core topics, regarding Mars and energy supplies to light bulb. Did anyone get 7.48 joules??? Or am I wrong

I rounded to 1.s.f because the question gave 2kg so 7 Joules

 

[Spoderman19]

That's the idea of a universal motor. The split-ring reverses the current direction (so keeps the current in the rotor coil constant in direction) but the magnetic field reverses direction due to the AC (instead of the current changing direction of a normal DC motor) to keep the torque constant in direction.

 

[jazz519]

I think it was a pretty easy exam. I finished with plenty of time to spare. Here's a couple questions for everyone:

What did everyone use for their three discoveries including the electric generator?
Did anyone else freak out when they saw eV and didn't know what it was?
For the solar panel multiple choice question, does light create electron hole pairs or a pd between the PN junction?
For the last multiple choice question, with a DC motor connected to an AC power supply, does it vibrate to the frequency of the AC or does it alternate a half turn backwards and forwards?
For the makeshift light source of Mars, what happens when the switch is open?

Cheers.

When the switch is open the rotor coil in the AC generator still experiences a change in magnetic flux which induces an emf, BUT because the circuit is not closed no current can form and therefore the light bulb does not glow