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# AQA Physics PHYA1 - 24 May 2016 - RESIT [Exam Discussion Thread] Watch

1. Can we all create an unofficial mark scheme qs + answers
1) isotope - same no. protons, diff no. neutrons
92*1.6*10^-19/mass no. * 1.67*10^-something I got 3.7 * 10^something
3 electrons removed to 89
fill in - mass number stays the same, 93 protons, 0, -1 for beta minus particle and antineutrino

Kind of forget the rest lol everyone pitch in!
2. (Original post by Tayeb)
Question said ION not atom. So you had to divide the charge by the charge of the electron. So 3 electrons.
The number of electrons in the ion will then be 89...
3. What did people put for the "how can this characteristic be used to work out the resistance of the diode between A and B" or something like that? I actually left it blank because I couldn't think of a thing!

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4. Or am I wrong?
5. (Original post by RUNSran)
I used the Vrms lost in the wires and their total resistance ( i assumed they were in series)
I think the vrms in the wires was like 0.5 something
I did something similar but had two wires in parallel as its 1 cable with the two wires side by side so got 229.5 v
6. (Original post by cowie)
What did people put for the "how can this characteristic be used to work out the resistance of the diode between A and B" or something like that? I actually left it blank because I couldn't think of a thing!

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Reverse the cell
7. (Original post by Tayeb)
Question said ION not atom. So you had to divide the charge by the charge of the electron. So 3 electrons.
The atom lost 3 electrons so there were 89 electrons in the ion.
8. (Original post by TajwarC)
Reverse the cell
I put reverse the diode, I'm not sure if I'll get the marks.
9. (Original post by JamieP123)
The atom lost 3 electrons so there were 89 electrons in the ion.
RIP. There's another mark lost :/ GAH I really wanted 120 :/
10. (Original post by TheLifelessRobot)
I put reverse the diode.
Same thing surely xD
11. If people want I can explain the heater question.
12. (Original post by TheLifelessRobot)
I put reverse the diode, I'm not sure if I'll get the marks.
Should be the same thing. Still reversing the current.
13. (Original post by Einstein1997)
The pd (5 volts) when the circuit is connected is Emf minus voltage over internal resistance. You're thinking of it the wrong way round.

Emf is the terminal pd when there's no current. When current flows the terminal pd is Emf - Ir
Brilliant. That's what I thought.

(Original post by Anon-)
ay what did you guys put for what the highest dot is in the oscilloscope reading? i put emf. teacher thinks it's terminal PD.
The emf can be defined as the potential difference across the terminals of a voltage source when no current is running. Therefore, you would both be correct.

(Original post by Einstein1997)
The pd across the terminals (5V) is the emf - internal resistanceThe internal resistance was 1V
I put something along the lines of 'it can get really hot during and after the experiment so the student should not touch it directly as it could burn his/her skin.' Fingers-crossed.

(Original post by sjmurkin)
The decay is K^+ = pi^+ + pi^0.If you look at their rest energies, K^0 has a higher rest energy than K^+, so it is not possible to create this from the decay of pi^0.I agree that it seems like K^0 could have been a possibility due to the wording of the question, and how it's possible to expect strangeness to be conserved, but unfortunately pi^0 is the only possible answer. However 2/3 of the marks should be for working out the charge and the fact it is a meson, not a baryon or lepton.
Would I still get 1-2 marks awarded if I had drawn a table with the baryon number, lepton number and charge under the particles in the equation?
14. (Original post by HARRY108)
Can we all create an unofficial mark scheme qs + answers
1) isotope - same no. protons, diff no. neutrons
92*1.6*10^-19/mass no. * 1.67*10^-something I got 3.7 * 10^something
3 electrons removed to 89
fill in - mass number stays the same, 93 protons, 0, -1 for beta minus particle and antineutrino

Kind of forget the rest lol everyone pitch in!
Questioned asked for the charge of the atom not the specific charge so you should have done 92*1.6x10^-19 which have your answer with units C

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15. The heater one, surely they have to be in series not in parallel? If they're parallel and there's only one cable then the circuit wouldn't be connected..
16. (Original post by JamieP123)
If people want I can explain the heater question.
17. (Original post by JamieP123)
If people want I can explain the heater question.
That would be helpful, I was very stumped on it

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18. X was definitely a neutral pion as all baryons decay through the weak interaction and therefore strangeness is not conserved. A very similar question came up in the June 2014. I put K^0 so I definitely lost a mark there
19. 7) current=0.28, Internal resistance = 3.6 ??. Also what was the quantity represented by thee 6V? EMF or Terminal pd?
20. For the heater question, the wires were in parallel right???
from that i worked out the rms voltage across the heating component to be 229.5V

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