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**Physics...Before/After**

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12467…16

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    #92
    Dwellingdweller
    Closed Accounts Posts: 825 ✭✭✭Dwellingdweller


    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.


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    #93
    Dwellingdweller
    Closed Accounts Posts: 825 ✭✭✭Dwellingdweller


    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?


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    #94
    Chuchoter
    Registered Users Posts: 4,306 ✭✭✭Chuchoter


    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


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    #95
    RedTexan
    Registered Users Posts: 217 ✭✭RedTexan


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


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    #96
    Chuchoter
    Registered Users Posts: 4,306 ✭✭✭Chuchoter


    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


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    #97
    RedTexan
    Registered Users Posts: 217 ✭✭RedTexan


    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?


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    #98
    Dwellingdweller
    Closed Accounts Posts: 825 ✭✭✭Dwellingdweller


    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?


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    #99
    Dwellingdweller
    Closed Accounts Posts: 825 ✭✭✭Dwellingdweller


    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? :confused:


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    #100
    Chuchoter
    Registered Users Posts: 4,306 ✭✭✭Chuchoter


    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?


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    #101
    Chuchoter
    Registered Users Posts: 4,306 ✭✭✭Chuchoter


    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? :confused:

    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?


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    #102
    Bears and Vodka
    Registered Users Posts: 2,249 ✭✭✭Bears and Vodka


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

    1) change in emf 2) change in resistance?


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    #103
    Dwellingdweller
    Closed Accounts Posts: 825 ✭✭✭Dwellingdweller


    Chuchoter wrote: »
    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?

    That'd actually be class if you could :D ATM I'm just finishing learning off the definitions from here but some proper notes would rock!

    And yeah, my mind was blown when I found out Lenz's Law was an example of Newton's Third Law too. Pretty cool stuff. :D The emf inducing the current, and the back emf opposing the emf that produced it, is actually an example of an action-reaction pair. :) Fascinating like
    subz3r0 wrote: »
    1) change in emf 2) change in resistance?

    Loving the conciseness of that answer :P Definitely gona write that one down.

    Q: What is the photoelectric effect? Give an application of it.


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    #104
    J.new
    Registered Users Posts: 26 ✭J.new


    What way do ye learn the experiments? By doing past papers or just writting them out on flashcards? Really struggling with them.

    Oh and we don't need to use a ruler when drawing diagrams?


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    #105
    Bears and Vodka
    Registered Users Posts: 2,249 ✭✭✭Bears and Vodka


    Dwellingdweller wrote: »
    Q: What is the photoelectric effect? Give an application of it.

    Photoelectric effect is the emission of electrons from the surface of a metal as light of a suitable frequency falls on to it.

    Automatic door sensors are an example of the photoelectric effect.

    :)


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    #106
    Liveforrugby
    Registered Users Posts: 343 ✭✭Liveforrugby


    Dwellingdweller wrote: »
    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?

    549313_235466626561724_232106568_n.jpg


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    #107
    BL1993
    Closed Accounts Posts: 341 ✭✭BL1993


    Liveforrugby wrote: »
    549313_235466626561724_232106568_n.jpg
    Robot arm all over again.


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    #108
    mathstalk
    Registered Users Posts: 162 ✭✭mathstalk


    For anybody in a hurry, I analysed the Section A's of the past papers a few months back, so here goes…
    Firstly, revise the speed of sound in air experiment, it hasn't yet come up in the 10 years of the course. I'd also recommend going over:
    1. The resistivity of a nichrome wire experiment,
    2. Verification of Joules law (by I^2 is proportional to delta theta),
    3. Specific latent heat of fusion of ice (By melting ice in water in calorimeter),
    4. Finding the value of small g (ball falling from electromagnet through trapdoor),
    5. Proof that frequency is inversely proportional to length in a stretched string (Paper rider+tuning forks+blocks),
    6. Investigation of the conditions of equilibrium for a set of co-plane forces (ruler+weights+Newton metres),
    7. The specific heat capacity of a metallic conductor (metallic conductor and thermometer in oil+heating element+joulemeter),
    8. Finding the period of a pendulum (easy),
    9. Finding the focal length of a converging mirror (guessable really)
    10. Finding the relationship between the voltage/ current in a semiconductor. (For metallic conductor/ bulb/ liquid experiments just switch the diode with something else on your diagram, duh.)
    These are the most likely to come up, so if your fúcked then look over these first. If 3 don't come up on the exam then ask for some rough work paper, wait till' the end of the exam to answer the risky question and as you answer the other questions, if anything pops into your head jot in down onto the rough work paper (I did this when Kavanagh came up in the English. By the last 40 minutes of the exam, I had accumulated a page full of quotes that had randomly popped into my head and was able to answer the question quite well).

    For most of the experiments, you don't need to learn off the graphs, you just have to ask yourself one question before drawing the graph: "What would the slope of this graph give me?" If the slope does not produce anything asked for in the question (I.e. Resistance/ acceleration due to gravity) then draw a graph that does.


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    #109
    BL1993
    Closed Accounts Posts: 341 ✭✭BL1993


    Speed of sound came up in 2006. :L However, I think it is gonna come up aswell


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    #110
    RedTexan
    Registered Users Posts: 217 ✭✭RedTexan


    J.new wrote: »
    What way do ye learn the experiments? By doing past papers or just writting them out on flashcards? Really struggling with them.

    Oh and we don't need to use a ruler when drawing diagrams?
    You need to use a ruler any time you draw light rays, otherwise you are suggesting that light doesn't travel in straight lines which would be wrong!


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    #111
    Dwellingdweller
    Closed Accounts Posts: 825 ✭✭✭Dwellingdweller


    Liveforrugby wrote: »
    549313_235466626561724_232106568_n.jpg

    No harm in testing ye on your general physics knowledge either. :D It's good to know how these things interact. :)


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    #112
    Liveforrugby
    Registered Users Posts: 343 ✭✭Liveforrugby


    BL1993 wrote: »
    Speed of sound came up in 2006. :L However, I think it is gonna come up aswell

    Most definitely, people won't do it though


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    #113
    Liveforrugby
    Registered Users Posts: 343 ✭✭Liveforrugby


    BL1993 wrote: »
    Robot arm all over again.

    Did you get robot arm?


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    #114
    BL1993
    Closed Accounts Posts: 341 ✭✭BL1993


    Liveforrugby wrote: »
    Did you get robot arm?
    Lol. No. :L I want to slap the guy who put it up with a robot arm though. :)


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    #115
    Liveforrugby
    Registered Users Posts: 343 ✭✭Liveforrugby


    BL1993 wrote: »
    Lol. No. :L I want to slap the guy who put it up with a robot arm though. :)

    My thoughts exactly, you think you still might of gotten the A1?


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    #116
    BL1993
    Closed Accounts Posts: 341 ✭✭BL1993


    Liveforrugby wrote: »
    My thoughts exactly, you think you still might of gotten the A1?
    Its borderline. Based on the solutions of paper 1 posted. I should have gotten 99% in P1 so if I do get it, I will only get it just. What makes me mad is that i was just about to get the right value for k for the circle question (only had to solve quadratic using -b formula) and thought i was doing it wrong. :s And I mssed up the part a in Q8 by forgetting to subtract 80 from 180 to get beta and messed up the graph at the end by forgetting about the semi circles :S

    Hopefully I'll get it. :S


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    #117
    Liveforrugby
    Registered Users Posts: 343 ✭✭Liveforrugby


    BL1993 wrote: »
    Its borderline. Based on the solutions of paper 1 posted. I should have gotten 99% in P1 so if I do get it, I will only get it just. What makes me mad is that i was just about to get the right value for k for the circle question (only had to solve quadratic using -b formula) and thought i was doing it wrong. :s And I mssed up the part a in Q8 by forgetting to subtract 80 from 180 to get beta and messed up the graph at the end by forgetting about the semi circles :S

    Hopefully I'll get it. :S

    Yea I got the 80 for beta, hopefully it's only a blunder... if you got 99 in paper 1 and the circle and bionic arm were the only problems, looks like an A1 to me :D


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    #118
    BL1993
    Closed Accounts Posts: 341 ✭✭BL1993


    Liveforrugby wrote: »
    Yea I got the 80 for beta, hopefully it's only a blunder... if you got 99 in paper 1 and the circle and bionic arm were the only problems, looks like an A1 to me :D
    Well it depends if they like my question 7 answers and how much marks I will accumulate in that Q8. My b and c parts were a disaster. If I would have done that triangle, graph and circle question right, I'd be at ease. :S

    Here's hoping. :s


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    #119
    RedTexan
    Registered Users Posts: 217 ✭✭RedTexan


    BL1993 wrote: »
    Well it depends if they like my question 7 answers and how much marks I will accumulate in that Q8. My b and c parts were a disaster. If I would have done that triangle, graph and circle question right, I'd be at ease. :S

    Here's hoping. :s
    This probably isn't the place but we're taking 3+2root2 to be the value for k right?


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    #120
    BL1993
    Closed Accounts Posts: 341 ✭✭BL1993


    RedTexan wrote: »
    This probably isn't the place but we're taking 3+2root2 to be the value for k right?
    Yes.


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    #121
    RedTexan
    Registered Users Posts: 217 ✭✭RedTexan


    BL1993 wrote: »
    Yes.
    Yera, I wouldn't be too worried, figures this year people 1 will be the one that will be defining. The former vice principal of my school is the assistant chief examiner and he said that if you wrote anything at all down for any question the likelihood is that you will get 5 marks upwards! And sure hey, there's bigger fish to fry next Monday!


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