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PHYA1 - Physics Unit 1 Exam - 24th May 2011

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Reply 120

tommowg

Original post by melon 314

i put strangeness is only conserved in the strong interaction for that question didn;t have a clue :smile:

guessing i won't be getting any marks for that

I put that too, and that other particles conserve all their properties in the weak interaction unlike strange particles :smile:

Reply 121

bubblebuddy

I feel like it went quite well

Besides the vertical line oscilloscope and the why does terminal pd decrease, it was straightforward.

Reply 122

A level Az

Original post by Limitless

Which direction was the W+ boson I put and arrow pointing left.

Right I think? going away from the neutron.

Yes it is I've just checked in my book. W+ going right, though I'm sure you may have been able to put a W- going left.

Reply 123

hwalker37

Original post by Limitless

Which direction was the W+ boson I put and arrow pointing left.

It was too the right, a W- boson to the left would have been correct though as it is the same as a W+ to the right

Reply 124

beelz

Original post by anil10100

Yeah for negligible resistance I drew the line y=1.52.
So I got the EMF as 1.52.
I got resistance as the negative gradient so 0.453, rounded to 0.45.
The line B, I put as having twice the gradient as internal resistance doubled. So the gradient was -0.9 and y-intercept remains 1.52.

For the last question I got overall resistance as 5Ohms (10/2).
Then the next bit was just resolving the 3Ohm resistors until it equalled 5Ohms.
For the last 2 I got, 1.3A(2sf) and 2V although I'm unsure on these.

The decay was electron capture, Feynman diagram had a W+ boson, neutron, and neutrino.

The second out of the two reactions was impossible as lepton number wasn't conserved (0--> -2)

Unsure why the terminal potential difference increased as amps increased.

Two baryons: neutron & proton.

Strange particles have strange quarks.

First oscilloscope trace was a dot 2 boxes above original.
Vertical line because time base was off so no horizontal movement, and it's moving up and down so fast it appears a vertical line.

6 marker was describing excitation then deexcitation, and explaining how the lines were discrete because of only certain wavelengths therefore frequencies therefore energy were possible as only certain energy photons can be emitted as there are only discrete energy levels the electron can de-excite through.

S'all I remember, I'm open to correction, hope it helps :smile:

*Decreased

And I wasn't very good at explaining it, but as the terminal PD decreases the Lost PD in the cell increases, and since the resistance in the cell is constant, if PD increases in the cell, the current must increase aswell to keep the resistance the same (because R=V/I).

Reply 125

Mr XcX

Really worried about exam now.

I have messed up the circuit question. :frown:

Reply 126

Naum

Original post by anil10100

Unsure why the terminal potential difference increased as amps increased.

That battery gives energy per unit charge (Joules/Coulomb). Increasing the current means that there are more coulombs of charge flowing through each second, therefore more energy is given (Joules/Coulomb -> Joules/Coulomb*100 or so..). This means that the terminal voltage decreases as more voltage is needed to drive the coulombs of charge around the circuit with the same joules/coulomb.

Hope that makes sense.

Reply 127

Gijoe123

can someone post the exam paper please

Reply 128

Limitless

Original post by hwalker37

It was too the right, a W- boson to the left would have been correct though as it is the same as a W+ to the right

Oops.

Reply 129

rub em out

Original post by Limitless

It was strange quark.
You might get the mark for anti strange but I think it was asking generally not specifically. So a particle is strange if it contains a strange quark.

I thought about putting strange quark, in the end i thought that was too easy so i put that strange particles include pie mesons in their decay

Reply 130

hwalker37

Original post by Limitless

Oops.

I shouldn't worry, only 1 mark lost :smile:

Reply 131

A level Az

What did people get for the specific charge of the helium/alpha particle?

Reply 132

Limitless

Original post by hwalker37

I shouldn't worry, only 1 mark lost :smile:

A mark here a mark there it adds up :frown:

Reply 133

Naum

Original post by A level Az

What did people get for the specific charge of the helium/alpha particle?

4.79 * 10^7 or something

Reply 134

AlesanaWill

I found the exam better than some years. There was no 'design an experiment' question which I was glad about, because I suck at those. Disappointed there was nothing on the photoelectric effect.

Overall I'd say it was an average paper, no easier or more difficult than any others. One or two of the questions seemed to be worded a little strangely though, including the 'strangeness' question. xD