Physics...Before/After

cocopopsxx · 13-06-2012 4:16pm

Thanks robbie, you too.

robbiep94 · 13-06-2012 9:13pm

cocopopsxx wrote: »

Thanks robbie, you too.

How do you know my name:rolleyes:;)

cocopopsxx · 13-06-2012 9:56pm

robbiep94 wrote: »

cocopopsxx wrote: »

Thanks robbie, you too.

How do you know my name:rolleyes:;)

Haha guessed it from the username. Hope I'm right.

Mr. Tambourine Man · 13-06-2012 11:45pm

For the 20 millionth time, this site and especially this page, is savage

http://www.thephysicsteacher.ie/leavingcertphysicsrevision.html

You can save all those documents as PDFs instead of printing them out very easily by doing

Save as
Save as type
PDF

I find printing off the syllabus useful also..

Now to actually learn everything!

Nitsuj · 14-06-2012 12:48pm

4 days to learn the course.
For electricity I'm only doing capacitance, since that hasn't been up in ages. For mechanics, I dunno if I'll do anything. **** it.
I'll learn the exps really well, I'll know modern, particle, heat, waves/sound/light really well and I'll hope q5 is alright. From looking at most of the past papers, you could get away without doing mechanics and electricity.

acorn1702 · 14-06-2012 12:54pm

Make sure you know Simple pendulum experiment, G by free fall and the forces experiment.

Bears and Vodka · 14-06-2012 1:13pm

Heat experiment is due to come up. They always have a heat question one year, then heat experiment the next and so on. Worth looking at them. Remember, experiments are worth 30% and they are fairly predictable and easy 30% so look over all of them.

cocopopsxx · 14-06-2012 1:33pm

Is the particle physics option worth it? My teacher didn't do it with us but he gave us the notes- looks fairly daunting but I've heard the questions aren't that bad. How long does it take to do it approximately?

As well, I haven't touched physics since morning, I'm just so scared of it.

where should I start? Gahhhh! I'm a confused soul

Epsi · 14-06-2012 1:40pm

cocopopsxx wrote: »

Is the particle physics option worth it? My teacher didn't do it with us but he gave us the notes- looks fairly daunting but I've heard the questions aren't that bad. How long does it take to do it approximately?

As well, I haven't touched physics since morning, I'm just so scared of it. where should I start? Gahhhh! I'm a confused soul

For the mock I learnt the definitions and Experiments first. They're worth roughly half the exam depending on the questions you do. The definitions also help you to understand some of the questions asked on the paper.

Nitsuj · 14-06-2012 1:43pm

Experiments are 30% and I heard definitions are usually 10-14%, so you could get a pass if you get full marks in them.

Bears and Vodka · 14-06-2012 1:48pm

cocopopsxx wrote: »

Is the particle physics option worth it? My teacher didn't do it with us but he gave us the notes- looks fairly daunting but I've heard the questions aren't that bad. How long does it take to do it approximately?

It's very easy if you know modern physics well because it kind of follows on from that. I'd say it would take a couple of hours to get a grip on it. Learn the Cockroft & Waltons accelerator diagram, the nuclear equation for it (Li + H => He + He + Q), learn pair production, positrons, anti-particles, and then the confusing stuff at the end like baryons and mesons and make sure you know the Quark composition of a proton and a neutron.
Questions on particle physics are very straightforward.

Nitsuj · 14-06-2012 1:49pm

Our teacher spent a double class before the mocks doing particle physics and never really touched on it again. It's pretty simple and short. Not to mention, always a guaranteed question.

clio94 · 14-06-2012 6:22pm

Id recommend having all the experiments perfect .. Expecting joules this year

Also learn all the derivations, definitions & non mandatory experiments - these come up every year and are usually worth about 30 marks.

You can't really predict much, better off just having a clear understanding of everything!

jos360 · 14-06-2012 7:31pm

If anyone needs a summary of modern physics!
The text is mirrored tho, sorry

Dicksboro_man · 14-06-2012 9:41pm

Lads, anyone know how physics is marked if you're asked for, lets say,an example of a use for a concave lens or something.. and you give two answers, of which only one is right. Is it gonna be like biology, where each wrong answer cancels out 1 right one, or is it gonna be like maths where they look at it as 2 attempts and they count your best one?

Bears and Vodka · 14-06-2012 10:20pm

They correct your first attempt and that's it.

Nitsuj · 14-06-2012 10:21pm

subz3r0 wrote: »

They correct your first attempt and that's it.

dammit

mathstalk · 14-06-2012 10:36pm

subz3r0 wrote: »

They correct your first attempt and that's it.

What if you write your answer in a way so that there is no definite "first attempt"?

For example:

EDIT: This is a serious question by the way.

Jimdwyer · 14-06-2012 10:47pm

cocopopsxx wrote: »

Is the particle physics option worth it? My teacher didn't do it with us but he gave us the notes- looks fairly daunting but I've heard the questions aren't that bad. How long does it take to do it approximately?

If you have the time it could be worth it as it's quite predictable but if not I think you should focus on perfecting what you know already

Dwellingdweller · 14-06-2012 10:50pm

I really wish the teachers in my school would teach things in a more exam-oriented way. Like, in Physics, we didn't do one test paper in class in two years. 95% of classes consisted of us sitting half-asleep listening to our teacher read notes from the textbook. Probably the worst way to learn Physics imaginable. Seriously, if I was teaching Physics I would print off the physicsteacher.ie stuff, do exam paper questions every day with the class, and then by the time the exam came around, they'd be certified A-grade students.

Reading notes from a textbook is the worst way to approach subjects for the LC, there's just so much detail that's not needed and which isn't accounted for in the marking scheme. Colossal waste of time on my teachers' part.

Bears and Vodka · 14-06-2012 10:57pm

mathstalk wrote: »

What if you write your answer in a way so that there is no definite "first attempt"?

For example:

EDIT: This is a serious question by the way.

In relation to that particular question my (very good) physics teacher says: 'Circular accelerators produce higher energy collisions' is a much better answer because it's a scientific explanation. 'Take up less space' is a general statement, take up less space, so what like? It has nothing to do with physics.

Wanchor · 14-06-2012 10:57pm

Here's a Chief Examiners report on Physics higher level. Yep, kinda bored.

Dwellingdweller · 14-06-2012 11:10pm

Does anybody know if, when they ask you to define the Newton, they'd accept something like this?

Define the Newton.
The newton is the kilogram per metre squared. (kgms^-2)

Or would that get no marks?

RedTexan · 14-06-2012 11:18pm

1 newton is that force which gives an object of mass 1kg an acceleration of 1m\s^2. probably best off sticking with the definition

mathstalk · 14-06-2012 11:18pm

Dwellingdweller wrote: »

Does anybody know if, when they ask you to define the Newton, they'd accept something like this?

Define the Newton.
The newton is the kilogram per metre squared. (kgms^-2)

Or would that get no marks?

I don't think the Newton is the kilogram per metres squared, if anything, it would be the kilogram per metres seconds squared. I'd stick to the plain definition though:

The Newton is the force that gives a mass of 1kg an acceleration of 1ms^-2

Dwellingdweller · 14-06-2012 11:22pm

RedTexan wrote: »

1 newton is that force which gives an object of mass 1kg an acceleration of 1m\s^2. probably best off sticking with the definition

mathstalk wrote: »

I don't think the Newton is the kilogram per metres squared, if anything, it would be the kilogram per metres seconds squared. I'd stick to the plain definition though:

The Newton is the force that gives a mass of 1kg an acceleration of 1ms^-2

It's definitely the kgms^-2 as well, but I think I'll stick to the plain definition if it comes up, in case the other way isn't on the marking scheme. Thanks

mathstalk · 15-06-2012 4:25pm

Demonstrative and mandatory experiments revised (Well, other than the ones that came up last year

)

Dwellingdweller · 15-06-2012 5:11pm

Hey guys, what's the importance of the depletion layer in p-n junctions? I know that negative electrons flow from the n to the p layer, and the positive free holes, as there's a potential difference between the layers but I don't understand where the depletion layer comes into play.

Osric · 15-06-2012 5:28pm

Prevents current flowing based on how diode is connected in circuit (forward-biased or reverse). If reverse-biased, depletion layer thickened - even less free charge carriers. If forward-biased, depletion layer reduced as opposite charge forced into each end, cancelling it out and allowing current to flow

I think

RedTexan · 15-06-2012 5:29pm

Dwellingdweller wrote: »

Hey guys, what's the importance of the depletion layer in p-n junctions? I know that negative electrons flow from the n to the p layer, and the positive free holes, as there's a potential difference between the layers but I don't understand where the depletion layer comes into play.

For a the semi-conductor to conduct there must be a voltage supplied which is greater than the depletion layer (and it has to be in forward bias of course), if the semi-conductor is connected in reverse bias the depletion is broadened. There are no charge carriers available in the depletion layer, when the depletion layer is overcome a large current can flow. That's pretty much the lot

Dwellingdweller · 15-06-2012 5:33pm

RedTexan wrote: »

For a the semi-conductor to conduct there must be a voltage supplied which is greater than the depletion layer (and it has to be in forward bias of course), if the semi-conductor is connected in reverse bias the depletion is broadened. There are no charge carriers available in the depletion layer, when the depletion layer is overcome a large current can flow. That's pretty much the lot

Ah! So the base voltage required for current to flow in the semiconductor has to overcome the PD depletion layer. And if connected in reverse bias, because the positive holes are attracted to the negative current flowing into the anode, and the negative electrons are attracted to the positive current flowing into the cathode, the depletion layer broadens. I get it! Thanks

RedTexan · 15-06-2012 5:34pm

And that's the reason only dc can flow in a diode! Because current flow only one way through the semi-conductor

mathstalk · 15-06-2012 6:10pm

Here's something you can print out to test your knowledge of definitions and figure out which ones to work on.

HeaneyBabe · 15-06-2012 6:22pm

I'm so screwed. I just can't get anything. What;s the best way to study?

water_piano · 15-06-2012 6:23pm

HeaneyBabe wrote: »

I'm so screwed. I just can't get anything. What;s the best way to study?

Without the Internet

15-06-2012 6:32pm

Considering going back to pass for Physics. Anything to look out for on the paper that's different to Higher Level?

Chuchoter · 15-06-2012 7:16pm

RedTexan wrote: »

And that's the reason only dc can flow in a diode! Because current flow only one way through the semi-conductor

No, AC can flow through a diode. It acts as a rectifier. DC can only flow through a diode in forward bias.
Also
A newton is that force that gives 1 kg an acceleration of 1ms^2

Wesc. · 15-06-2012 7:18pm

I've decided to do the whole course apart from experiments tomorrow. Don't know how I'll cope.. but I have two bottles of red bull in preparation!

Chuchoter · 15-06-2012 7:20pm

We should post questions to test eachother because I have no ****ing clue what to look at anymore.
First question:
What can affect the accuracy of the stretch string experiment?

Nitsuj · 15-06-2012 7:22pm

Just asked a question on 2xm about the marking and they said they give the best attempt UNLESS you have two contradicting answers, like you state that the neutrino is positive and negative.

Dwellingdweller · 15-06-2012 7:23pm

Chuchoter wrote: »

No, AC can flow through a diode. It acts as a rectifier. DC can only flow through a diode in forward bias.
Also
A newton is that force that gives 1 kg an acceleration of 1ms^2

ms^-2*

AC is turned into DC when it passes through a diode, is it not? Like, both AC and DC current can flow through a diode, but when they come out they both have to be DC.

Dwellingdweller · 15-06-2012 7:24pm

Chuchoter wrote: »

We should post questions to test eachother because I have no ****ing clue what to look at anymore.
First question:
What can affect the accuracy of the stretch string experiment?

Parallax or zero error.
Always. No exceptions. :P Hahah, what's the answer?

Chuchoter · 15-06-2012 7:25pm

Dwellingdweller wrote: »

ms^-2* AC is turned into DC when it passes through a diode, is it not? Like, both AC and DC current can flow through a diode, but when they come out they both have to be DC.

I was just testing you :P

As far as I can remember its like the bottom half of the sine wave gets chopped off because it can go in one way and when it tries to come back it gets stuck? Does that make it DC

RedTexan · 15-06-2012 7:27pm

Yeah, it's DC when it comes out, that's what I meant by saying AC can't flow through yano?

Chuchoter · 15-06-2012 7:27pm

Dwellingdweller wrote: »

Parallax or zero error.
Always. No exceptions. :P Hahah, what's the answer?

Those two! And tuning forks are easily damaged so the frequency may not be the one stamped. Also, very high frequencies mean tiny wavelengths means increased percentage error.

Ask another question!
I fell asleep at my desk today trying to do physics so this is making up for it :P

RedTexan · 15-06-2012 7:34pm

Really is there much else new that they can ask which they haven't asked before? I've been through the exam papers an good few times and it seems to me all that they haven't asked before is a small bit on ring and radial circuits and maybe the experiment to find the refractive index use real and apparent depths. Last year they went pretty much all out on new stuff they haven't asked, it's hard to see anything else they might ask?

Dwellingdweller · 15-06-2012 7:38pm

Chuchoter wrote: »

I was just testing you :P

As far as I can remember its like the bottom half of the sine wave gets chopped off because it can go in one way and when it tries to come back it gets stuck? Does that make it DC

Those two! And tuning forks are easily damaged so the frequency may not be the one stamped. Also, very high frequencies mean tiny wavelengths means increased percentage error.

Ask another question!
I fell asleep at my desk today trying to do physics so this is making up for it :P

I think that's it! The way I think of it is that there's actually two waves travelling around the circuit simultaneously, one negative and one positive, the negative current flows into the N-layer so it doesn't pass through and only the positive current flows through.

Full-wave rectification is when the diodes are arranged so the negative gets squeezed into the positive axis and comes out as 'smoothed' (using a capacitor) on the oscilloscope.

Q: How is Lenz's Law an example of Newton's Third Law in Electricity?

Dwellingdweller · 15-06-2012 7:43pm

Oh shíte! Just realised I haven't done anything on Fission/Fusion/Nuclear Energy since I've started doing Physics. Dunno if it's vital to do though, I've covered everything (including my option, Applied Electricity) so far except for it so I'll probably just do a quick scan over it. Does a full question on it come up every year?

Chuchoter · 15-06-2012 7:47pm

Newtons 3rd law states that every action has an equal and opposite reaction.
A changing magnetic flux cutting a coil causes an emf to be induced. Lenzs law tells us that the direction of the emf will attempt to oppose this change. Thus, if we take the changing emf as the action, the opposing direction of the emf is an equal and opposite reaction.

(When I first saw that I was like **** NEWTON HAD LAWS OF ELECTRICITY TOO?!) :P

Q: What is the thermometric property of a 1) thermocouple and 2) a thermistor?

Chuchoter · 15-06-2012 7:48pm

Dwellingdweller wrote: »

Oh shíte! Just realised I haven't done anything on Fission/Fusion/Nuclear Energy since I've started doing Physics. Dunno if it's vital to do though, I've covered everything (including my option, Applied Electricity) so far except for it so I'll probably just do a quick scan over it. Does a full question on it come up every year?

I don't think it has to, but I'd have a flick through it because its really easy. I made loads of notes the other day I could send them to you if you'd like?

**Physics...Before/After**

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Physics...Before/After