General 2k16 Physics Discussion!

[Adequace]

For Sound MCQ, what did everyone get for Q7? I had to give an educated guess of D, my answer wasn't even an option but it seemed like it was the correct way to do it..

[Swagadaktal]

For Sound MCQ, what did everyone get for Q7? I had to give an educated guess of D, my answer wasn't even an option but it seemed like it was the correct way to do it..

Yeah - you had to find the path distance (exactly like you do with light for destructive interference)
N + 1/2 lamda, where n = 2, PD = 1.5m - then you had to find the distance from ea other. sooo (10-4.5) - 4.5 = 1.5, so had to be 4.5m away

[jkii007]

Does anyone have a copy of the exam or know when and where solutions will be posted?

[Swagadaktal]

How did you guys answer the open circuit question? The one where the LED is falty?

And with light intensity - the intensity couldnt go below x axis right coz its light? You can't have negatiev light intensity right?

But did it have to touch the x axis?

[jazzaa36]

What light intensity question ?!?!!!

[Swagadaktal]

What light intensity question ?!?!!!

The modulated wave that you had to draw

It was light intensity vs time graph

[jazzaa36]

Fkkkk didn't realise that ! I drew the variation in the neg and positive

For the led question, I wrote the current wouldn't flow through that set of lights hence the current will increase in the other other set of lights etc.. wby ?

[Striddawg]

How did you guys answer the open circuit question? The one where the LED is falty?

And with light intensity - the intensity couldnt go below x axis right coz its light? You can't have negatiev light intensity right?

But did it have to touch the x axis?

Open circuit LED question- I said it wouldn't work? Like I'm not the strongest physics student by any stretch but I said something about diodes causing like current control and said that this change in current caused by the faulty LED would cause the entire circuit to stop working, but I have very little confidence.
Regarding the light intensity modulation, I literally just lifted the original graph up but mine didn't touch the x-axis but again, little certainty x

[Adequace]

How did you guys answer the open circuit question? The one where the LED is falty?

And with light intensity - the intensity couldnt go below x axis right coz its light? You can't have negatiev light intensity right?

But did it have to touch the x axis?

The faulty LED would cause less resistance through that branch, therefore more current would flow through the 2nd branch since the total current of the circuit is unchanged.

For the light intensity one, you just had to shift the time variation of the input signal so it didn't become negative. If you drew it touching zero, it should still be fine.

Edit: did you draw in the carrier wave? I did, wasn't 100% if I had to.

[Swagadaktal]

The faulty LED would cause less resistance through that branch, therefore more current would flow through the 2nd branch since the total current of the circuit is unchanged.

For the light intensity one, you just had to shift the time variation of the input signal so it didn't become negative. If you drew it touching zero, it should still be fine.

I drew it not touching the x axis

is that fine?

[Adequace]

I drew it not touching the x axis

is that fine?

Yeah that's fine, it's what I did as well.

[HopefulLawStudent]

Anyone have a copy of the exam paper???

[Swagadaktal]

How about that geostationary question?

[jazzaa36]

Please tell me the voltmeter reading was 6v and the ammeter was half the current in R1 

[Zealous]

If anyone's got a copy of the exam paper it'd be great if you could create a new topic and post it there!

I don't have time to work the entire exam but maybe I can help clarify some of the more difficult questions.