Physics Aftermath

Thomas_S_Hunterson

carlowboy wrote:

galvonometer? I did a symbol for a micro ammeter ( like mewA)

I'm sure that would be accepted

JC 2K3

sean_keevey wrote:

For the graph of the reverse bias diode, you'd probably want to scale the Y axis in micro-amps as opposed to milliamps and use a galvanometer in the circuit instead of a milliammeter.

Or a microammeter, perhaps? You put it on the otehr side of the voltmeter too right?

And yeah, I scaled the Y axis in micro-amps, I didn't use graph paper though, since it only said "sketch", now I think it might have been a better idea to do it on graph paper after all....

sean_keevey wrote:

The junction voltage was 0.6V I think, I did quite a large graph for it and it was pretty much identical to a standard Si p-n graph, so that would add up nicely.

I reckon they'll look at your graph and if you've marked in how you got it they'll give you the marks.

Thomas_S_Hunterson

JC 2K3 wrote:

Or a microammeter, perhaps? You put it on the otehr side of the voltmeter too right?

It goes in the same place as the ammeter did, unless you're using a shunt, but I don't think there's any need for that given the minuiscule current.

carlowboy

sean_keevey wrote:

It goes in the same place as the ammeter did, unless you're using a shunt, but I don't think there's any need for that given the minuiscule current.

It doesn't go in the same place as the milliammeter, it gets connected closer to the diode so only the current going through the diode is measured instead of the current going through the voltmeter.

eZe^

sean_keevey wrote:

It goes in the same place as the ammeter did, unless you're using a shunt, but I don't think there's any need for that given the minuiscule current.

You change where the microammeter is when its in reverse bias, you connect it in series with the diode in reverse bias and put the voltmeter at either side of the circuit.

carlowboy

eZe^ wrote:

You change where the microammeter is when its in reverse bias, you connect it in series with the diode in reverse bias and put the voltmeter at either side of the circuit.

That expresses what I said far better.

DtotheK

Mushy wrote:

Ok, couldnt be bothered reading over 12 pages of stuff bout physics, so here goes my assessment of my Ordinary Level Paper:

Experiments: 2 of them I studied hard yesterday cos they've never come up, another one I reminded myself of just incase as its been a few years. Did experiments 1,2,4. Joules Law was a sweet one, definately full marks. Hopefully over the 100 mark barrier for Section A.

Q5: Ridiculously easy...apart from I couldnt remeber the exact definition for Newtons Second Law. Probably 52/56.

Q6: Ok, apart from that energy gained question, it went ok. I did an extra question, so they'll leave out my worst score, which will probably be this question. Probably 40/56

Q8: This was actually the extra question I did. didnt like the look of the diagram, so I left it, then at the end, I looked at it again and did it. Very, very easy, maybe apart from that detecting the radiation bit kinda. Probably50/56

Q10: I congratulate you SEC! You **** up the diagram of a bloody x-ray machine AGAIN. I mentioned it in one of my answers about how the diagram was wrong:p. Still though, should have gotten nearly full marks again here. Probably 52/56

Q11: My favourite! The little article...never looked at it. Still just so damn easy. Full marks here. 56/56

Q12: Did part (c) and (d). Relatively easy. Just one very stupid little mistake. I'd say it'll be in the high 40's, if not 50's for this. 48/56 at worst.

Overall: This exam will hopefully be an A1, but it'll be so damn close. Very borderline. The 60 marks would be sweet, especially to back up my accounting disaster.

I just shat myself reading this. I didn't read the first sentence...
WTF newtons 2nd law in Q5??? DAMN i new that why the **** didn't i see that!!!

Thankfully i coped on after a few minutes , other wise i wouldn't be able to sleep:(

Thomas_S_Hunterson

Sorry i had assumed that the ammeter was already directly 'beside' the diode. My mind is a bit of a mush...just coverered 75% of the chemistry course. Physics is a distant memory.

/edit wait I just looked at the question, it is not specified where the ammeter is when the diode is forward biassed. In theory it should be in the exact same place as when the diode is reversed, ie beside the Diode

eZe^

DtotheK wrote:

I just shat myself reading this. I didn't read the first sentence...
WTF newtons 2nd law in Q5??? DAMN i new that why the **** didn't i see that!!!

Thankfully i coped on after a few minutes , other wise i wouldn't be able to sleep:(

I thought she/he was taking the piss, I saw joules law so I was guessing that they were talking about 06!

sean_keevey wrote:

Sorry i had assumed that the ammeter was already directly 'beside' the diode. My mind is a bit of a mush...just coverered 75% of the chemistry course. Physics is a distant memory.

Ill have to go cover that in about 10 minutes... Oh god, wish me luck! ahahah

DtotheK

i should really stop visiting here nowadays...
i just get worried with all the post mortoms...

Esterfication and beyond!!!

eZe^

sean_keevey wrote:

Sorry i had assumed that the ammeter was already directly 'beside' the diode. My mind is a bit of a mush...just coverered 75% of the chemistry course. Physics is a distant memory.

/edit wait I just looked at the question, it is not specified where the ammeter is when the diode is forward biassed. In theory it should be in the exact same place as when the diode is reversed, ie beside the Diode

Oh, you were talking about forward bias?!?! In that case the voltmeter doesnt connect to the ammeter at all, it only measures the p.d between the diode.

Kwekubo

eZe^ wrote:

I put the piece of copper (connected to joulemeter) in a boiling tube of glycerol and heated it with a joulemeter... Found the final temperature and reading on joulemeter and then removed it from glycerol and added to the calorimeter... Seemed ok to me!

I just said I stuck it in a water bath until the temperature got to 100 celsius - opinions?

rjt

Mushy wrote:

Q11: My favourite! The little article...never looked at it. Still just so damn easy. Full marks here. 56/56

How'd you get 11(b) without reading the text? :P (and congratulations on the A).

Edit: n/m, I just saw 'ordinary level', sorry :P

When I first opened the paper, I thought "yes!" (in fact half of the exam hall made various approving noises). This lasted until we all looked at section B and/or question 2 (we all did the experiment the other way, had no idea about this method).

Luckily, there were just enough questions to get me through - I thought 5,7,9 and 12 were all do-able, and I think I should've managed an A.

Feddd

Kwekubo wrote:

I just said I stuck it in a water bath until the temperature got to 100 celsius - opinions?

I based it on the experiment to find the Shc of copper. Drew the diagram and said that its heated by the coil+glycerol in one hole and temp recorded by the thermometer +glycerol in the other hole.
Think that sounds ok? Didn't mention boiling tubes or boiling water like everyone else seemed to.

And in regards the quote: You explained how to heat it but you are also asked how to measure its temperature.

Tomlowe

little copper granules in the bottom of a beaker over a bunsen with a thermometer in... whats wrong with that

Kwekubo

Feddd wrote:

I based it on the experiment to find the Shc of copper. Drew the diagram and said that its heated by the coil+glycerol in one hole and temp recorded by the thermometer +glycerol in the other hole.
Think that sounds ok? Didn't mention boiling tubes or boiling water like everyone else seemed to.

And in regards the quote: You explained how to heat it but you are also asked how to measure its temperature.

Oh, well I said that too - thermometer. Everyone seems to have reacted differently to this in the heat of the moment!

Feddd

Kwekubo wrote:

Oh, well I said that too - thermometer. Everyone seems to have reacted differently to this in the heat of the moment!

Impressive pun, possibly referring to Q1 as well as Q2.

Gangsta

ZorbaTehZ wrote:

@Gangsta: Amplitude is the distance between the maximum displacement and the point of equilibrium, so by that logic it must be at 285mm - why do you think it could be 280mm? (so I can follow your train of thought)

oh sh!t, sorry dude I meant to say the pt of equilibrium is 285mm:o my bad.

Feddd

Question: Wasn't very familiar with Q4 as I hate electricity, but instead of having a poteniometer in the circuit I had a variable resistor and said that potential difference is altered by altering the resistor. Will I still get the marks do ye think?

JC 2K3

Yup.

As long as it's a source of varable voltage and is connected right you're grand.

adam_ccfc

I'm doing a rough addition of my marks and it is going to be pretty close for me!

Couple of very silly mistakes. I'll be in the range of about 88-94% somewhere.

amacachi

physics for me was the same as the rest of my subjects so far, its not that it was really hard, it was just awkward and the way the questions were put together really didnt maximise my marks. no-one to blame but meself tho

JC 2K3

adam_ccfc wrote:

I'm doing a rough addition of my marks and it is going to be pretty close for me!

Couple of very silly mistakes. I'll be in the range of about 88-94% somewhere.

Same here, I reckon I could dip to a B1, but if the marking scheme isn't strict I could be in A1 land.

Feddd

JC 2K3 wrote:

Same here, I reckon I could dip to a B1, but if the marking scheme isn't strict I could be in A1 land.

Exact same for me. I made 2 extremly retarded mistakes. In the theme question I completly missed the "Watts" in 300 giga watts and took it as 300giga watts a year, and in the mechanics question I took 315mm as the maximum displacement instead of 25mm which was the extention and also got the third part of that wrong cause I wasn't concentrating enough.

Made some more mistakes but they were genuine mistakes. The above ones are just silly slips which I should have known but wasn't focused enough and may cost me the A.

timmywex

http://www.examinations.ie/index.php?l=en&mc=en&sc=ep&formAction=subject


http://www.examinations.ie/archive/exampapers/2007/LC021ALP000EV.pdf


a link to the different papers...

Feddd

By the way, whats the policy in physics on carrying on mistakes? I know its usually 3 marks per line in a calculation, but if I put in a wrong number 1) Do I lose all 3 marks for that line where I substituted my values or just 1 or 2 if there were a few values to substitute? and 2) If I calculate the wrong numbers correctly do I get the marks after that line?(Usually 2 for calculation of the final line).
Someone please enlighten me because if its true then I may have gotten the A1 and I will be once again motivated to study for my remaining subjects!

E92

I think its like Maths, the same error in the same section is only penalised once ie, wherever you make the mistake you lose themarks there, but if get the 'right' answer ie you keep going with the wroing figures and work it out as best you can you'll get the rest of the marks.


I thought that paper was horrible, Q2 is too specific, as was mentioned by someone else here look at page 29 of the syllabus, and you'll se why, same goes for Q3, you dont jhave to do that experiment with a Graph, I spoke to people in my year who never did that experiment with a Graph(its not mandatory), we were lucky that our Physics teacher who finished the couse with us way back in November told us how to deal with the Graph if they asked it, Q6 was an Applied Maths question, very doable if you do that section of Applied Maths, but it muust habve been awful for everyone else. I actually thought it looked impossible at first(Q6), but then I looked again and realised that it was an Applied Maths kind of Question and that along with Q12 part a), which was also an Applied Maths type of Question(though a much easier Question than 6) saved my arse in Physics yesterday.

I dont really like Post Mortems too much, but does anyone know the answer to Q1 part ii) and iii), or more specifically, how they worked out the answer? I'm just curious as to what people did, cause mine didnt equal(you should get the same answer for both parts, shouldn't you), and I'd like to know where I went wrong.

carlowboy

E92 wrote:

I think its like Maths, the same error in the same section is only penalised once ie, wherever you make the mistake you lose themarks there, but if get the 'right' answer ie you keep going with the wroing figures and work it out as best you can you'll get the rest of the marks.


I thought that paper was horrible, Q2 is too specific, as was mentioned by someone else here look at page 29 of the syllabus, and you'll se why, same goes for Q3, you dont jhave to do that experiment with a Graph, I spoke to people in my year who never did that experiment with a Graph(its not mandatory), we were lucky that our Physics teacher who finished the couse with us way back in November told us how to deal with the Graph if they asked it, Q6 was an Applied Maths question, very doable if you do that section of Applied Maths, but it muust habve been awful for everyone else. I actually thought it looked impossible at first(Q6), but then I looked again and realised that it was an Applied Maths kind of Question and that along with Q12 part a), which was also an Applied Maths type of Question(though a much easier Question than 6) saved my arse in Physics yesterday.

I dont really like Post Mortems too much, but does anyone know the answer to Q1 part ii) and iii), or more specifically, how they worked out the answer? I'm just curious as to what people did, cause mine didnt equal(you should get the same answer for both parts, shouldn't you), and I'd like to know where I went wrong.

Agreeing with you apart from Q6. I don't do Applied Maths (was crap at it as I didn't put any effort in). If you knew omega^2=k/m, it was the easiest question on the paper.

adam_ccfc

I don't do applied maths, but I knew how to work that problem, so I was alright.

Feddd

E92 wrote:

I dont really like Post Mortems too much, but does anyone know the answer to Q1 part ii) and iii), or more specifically, how they worked out the answer? I'm just curious as to what people did, cause mine didnt equal(you should get the same answer for both parts, shouldn't you), and I'd like to know where I went wrong.

They came out perfectly equal for me and my friends.
You may have left out the weight of the meter stick? Only thing I can think of. I left it out aswell at first but when I was finished the exam and looking over it I relised it.

I do applied maths but don't cover the section that came up in Q6 but considering hookes hasn't come up in years I studied it well the night before and got lucky. I agree that it was applied mathsy considering there were so many marks for calculations. Made a few mistakes in it but hopfully wil be amrked easy as its probably the hardest part of the mechanics course.

Q12(a) was an absolute walkover for applied maths students though.