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OCR PHYSICS B G495~ 18th June 2015 AM ~ A2 Physics

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nvm
Original post by Iridann
Quite nice surprisingly. Probably just because I was must better prepared for the timing and way they ask questions this year.

You must be the only person I know to have found it okay, but I don't think I did too bad, I'll do so much worse on this one guaranteed
Original post by Mutleybm1996
How can you define a quark?
Other than a fundamental particle


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The building blocks of hadrons with fractional charge??

No idea, I assume just mention they're fundamental and have fractional positive and negative charges? :tongue:
Do we need to know the Millikan oil drop experiment equation or will it be given if it came up?
Do we have to know about W+/W-/Z0?


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Reply 145
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Original post by Mutleybm1996
Do we have to know about W+/W-/Z0?


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Only in general terms. They exist, they're bosons, they interact weakly. Other than that, nothing else.
Original post by Liam_Heathcote
Do we need to know the Millikan oil drop experiment equation or will it be given if it came up?


I think they just ask you to rearrange E=V/x or E=F/q with F=mg

so you get mg=Eq
Original post by Tibbz2
The building blocks of hadrons with fractional charge??

No idea, I assume just mention they're fundamental and have fractional positive and negative charges? :tongue:


Do they ha've half spin values?
Reply 148
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h4mz4
How do u work out wavelength of electron if u have h-6.6*10^-34 m- 9.1*10^-31 and also KE 2*10^-18

Thanks
I know the stuff on the pre release well but what background knowledge do we need for it? I have spent all my time revising the topics and not the pre release? Also how many marks worth of the pre release do you think will be stuff related to what is directly on the pre release and not requiring background knowledge
Original post by RealTime
It's similar to Young's double slit experiment where maxima and minima are formed due to diffraction. In this case the "slit" is a hole instead - the nucleus which the electrons are diffracted by (varying scattering angle), and a circular diffraction pattern forms. The minima forms due to the electrons acting as a wave and causing destructive interference and the waves are out of phase, cancelling eachother out. Maxima occurs when they are in phase and superposition occurs. They only give a bit of the graph, seeing more helped me link it to Young's double slit experiment and you can use ideas of that on here, just keep in mind that a circular pattern forms rather than a fringe.

(here's the full graph with picture of why it forms)


My answer avoids using phasors to explain it, I find it easier that way cos I find talking about phasors can get a bit confusing.


Thank you so much! This made is so much clearer and easier to understand. :smile:
Original post by Iridann
Do they ha've half spin values?


No, up quarks have +2/3 and down have -1/3 :smile:
Original post by Baylo97
I know the stuff on the pre release well but what background knowledge do we need for it? I have spent all my time revising the topics and not the pre release? Also how many marks worth of the pre release do you think will be stuff related to what is directly on the pre release and not requiring background knowledge


According to the specification, section C is approximately 40/100 marks whilst sections A and B are approximately 60/100 marks. Make of that what you will :smile:
Original post by h4mz4
How do u work out wavelength of electron if u have h-6.6*10^-34 m- 9.1*10^-31 and also KE 2*10^-18

Thanks


Isn't it just E=hf?


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Original post by Tibbz2
No, up quarks have +2/3 and down have -1/3 :smile:


Those are their charges :smile: I'm talking about spin values. https://en.wikipedia.org/?title=Quark#Spin

Turns out quarks do have half spin values.
Original post by h4mz4
How do u work out wavelength of electron if u have h-6.6*10^-34 m- 9.1*10^-31 and also KE 2*10^-18

Thanks


use 1/2 * mv^2 = hc/lambda
Original post by Mutleybm1996
Cheers


Could you quickly explain how a generator and motor work?
The electromagnetism stuff really confuses me


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Motors have a split ring commutator. And on each side there are two (opposite poles) of a permanent magnet. You know, hopefully, from the LHR that there will be a force upwards when the current is going from +ve to -ve. Therefore the motor turns steadily, once the 'shaft' is at 180 deg, the split ring commutator switches the current around so there's a force downwards. This process repeats over.

I think generator have a stator and a rotor, and the spinning rotor induces an emf (by Farday's law) into the stator. Usually they give you a bit of context in the question.

The more past papers I do the less prepared I feel, oh god.
Reply 157
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urz13
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How on earth do you calculate the emf from the gradient of the graph in Q11 part b) here?

Paper: http://moodle.flintshire.gov.uk/hhs/pluginfile.php/2360/mod_folder/content/0/Current%20Syllabus/G495%20June%2014.pdf?forcedownload=1
(June 2014 paper)

Thanks!
Original post by Iridann
use 1/2 * mv^2 = hc/lambda


You could just do:

λ=h2×m×KE \lambda = \dfrac{h}{\sqrt{2 \times m \times KE}}

where m is the mass
Reply 159
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STATER
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Does the Pauli exclusion principle mean that there can only be one electron at each energy level at any given time?

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