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# AQA Physics Unit 1 PHYA1 20th May 2013 Watch

1. (Original post by Son234)
Does a positron or an electron antineutrino have a lepton number of -1?

It doesn't say in my textbook

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Yep, this is on the formula sheet btw
2. (Original post by Son234)
Does a positron or an electron antineutrino have a lepton number of -1?

It doesn't say in my textbook

This was posted from The Student Room's iPhone/iPad App
Apart from rest mass Anti-particles have opposite properties. So they both have -1 because electrons and neutrons are 1
3. Could somebody please explain to me how to do question 6b in the Jan 2013 Unit 1 paper?

Specifically, for C-D. I just don't understand how you calculate voltage between two points, especially if they're between two parallel lines
4. (Original post by cyfer)
Could somebody please explain to me how to do question 6b in the Jan 2013 Unit 1 paper?

Specifically, for C-D. I just don't understand how you calculate voltage between two points, especially if they're between two parallel lines
It's because the pd at A-C is 6 And the pd at D-F is 4. C-D is between these two points, therefore the answer is 2 because 6-4=2 Remember its potential DIFFERENCE, the potential difference between these two points is 2 hence the answer is 2.
5. (Original post by lamp010101)
It's because the pd at A-C is 6 And the pd at D-F is 4. C-D is between these two points, therefore the answer is 2 because 6-4=2 Remember its potential DIFFERENCE, the potential difference between these two points is 2 hence the answer is 2.
Could the answer be negative though? You can get negative voltage in circuits, so how do you know if it is negative, which way it's going around? Or is this irrelevant?

Also when you say this, do you go around the top or the bottom of the circuit? Could you just as easily say D-B has 8V so 8-6=2? Again, which way would you go around?
6. (Original post by x-Sophie-x)
Yep, this is on the formula sheet btw
Oh yeah it is as well thanks

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7. I think its because on the diagram for question 6, voltage is flowing in a clockwise direction. At point D 8v has already been lost, hence there are only 4v left, point C is 6v so the values 4 and 6 are used to calculate the pd rather the 6 and 8. I don't think negative voltages are relevant as it depends on which was around the voltmeter is attached to the wires you may want to check this in the textbook though

EDIT: I think 8-6 would also work but I'd use the values already calculated as it seems as though they're leading us into the answer
8. Does anybody have a big list of electricity questions by chance?
9. On the markscheme for Jan 2013 why in question 7 does it want answers to 3sf when the question is in 2sf? would i lose marks for doing it properly and rounding to the correct accuracy??
10. (Original post by lamp010101)
I think its because on the diagram for question 6, voltage is flowing in a clockwise direction. At point D 8v has already been lost, hence there are only 4v left, point C is 6v so the values 4 and 6 are used to calculate the pd rather the 6 and 8. I don't think negative voltages are relevant as it depends on which was around the voltmeter is attached to the wires you may want to check this in the textbook though

EDIT: I think 8-6 would also work but I'd use the values already calculated as it seems as though they're leading us into the answer
At D, only 4V has been lost through the thermistor, not 8. The 10kOhm resistor has 8V flowing through it.

Going clockwise we would would have DF 4V and then AC 6V so it would 4-6=-2? Unless you do 8-6=+2V

Essentially I'm confused

(Original post by OliverG)
Does anybody have a big list of electricity questions by chance?
I second this!
11. (Original post by lamp010101)
I think its because on the diagram for question 6, voltage is flowing in a clockwise direction. At point D 8v has already been lost, hence there are only 4v left, point C is 6v so the values 4 and 6 are used to calculate the pd rather the 6 and 8. I don't think negative voltages are relevant as it depends on which was around the voltmeter is attached to the wires you may want to check this in the textbook though

EDIT: I think 8-6 would also work but I'd use the values already calculated as it seems as though they're leading us into the answer
How are we meant to know which one is R1 and R2 in potential divider calculations?

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12. (Original post by Goods)
On the markscheme for Jan 2013 why in question 7 does it want answers to 3sf when the question is in 2sf? would i lose marks for doing it properly and rounding to the correct accuracy??
Markschemes can have small discrepancies in significant figures. As long as you wrote out the full answer at some point in your workings, you will be given the mark UNLESS the question specifically asks you to quote the correct number of significant figures
13. (Original post by OliverG)
Does anybody have a big list of electricity questions by chance?
Hello. I need more practice on electricity questions myself because I still feel that I need more practise. I am fine with quantum and particle stuff but not electricity. However, my mathematical ability is really good but I just hate electricity lol! If you get any help from anyone or if you have more questions on electricity, please reply them to me ASAP since the exam is on 20th of may. Thanks!!!
14. (Original post by cyfer)
Markschemes can have small discrepancies in significant figures. As long as you wrote out the full answer at some point in your workings, you will be given the mark UNLESS the question specifically asks you to quote the correct number of significant figures
But this markscheme is appalling. On one question is says you get the mark for specifying the exact amount on energy for the n=1 to n=2 jump then proceeds to give the wrong value giving 10.1 instead of 10.19 (10.2 if correctly rounded). and then in question 4 you are working in 3sf provided you use raw data for your calculation and it asks for 2sf with no reason!!!
15. (Original post by OliverG)
Does anybody have a big list of electricity questions by chance?
Go through here and get the PHA3W papers.

http://www.freeexampapers.com/#A%20L...QA/Physics%20A
16. (Original post by IWantSomeMushu)
Go through here and get the PHA3W papers.

http://www.freeexampapers.com/#A%20L...QA/Physics%20A
Thanks! But older past papers than 2009 have radiation in them instead of electricity.
17. (Original post by cyfer)
At D, only 4V has been lost through the thermistor, not 8. The 10kOhm resistor has 8V flowing through it.

Going clockwise we would would have DF 4V and then AC 6V so it would 4-6=-2? Unless you do 8-6=+2V
Voltage doesn't actually have a direction it's just easier to think of it like that for this question. Also you can just ignore negative voltages as they are not on the spec, switching the terminals attaching the voltmeter would obtain a positive value anyway. The mark for that question is for the answer two, so as long as you get the answer you'll get the mark
18. (Original post by Jimmy20002012)
How are we meant to know which one is R1 and R2 in potential divider calculations?

Posted from TSR Mobile
It doesn't really matter as long as you use the corresponding voltage (ie v1 with R1) you should be fine
19. (Original post by Nav_Mallhi)
Some, not all of the stuff in on the data sheet.
I don't really have any tips for it, I just memorised them.

I presume that you have worked out the voltages for A-C (6V) and D-F (4) in the previous part so the question. Voltage is the potential DIFFERENCE. So all you do it 6-4 = 2V.

thanks a lot.

would really appreciate it if someone has a list of units they can share (mega, milli) and their conversions? thanks
20. (Original post by BenChard)
thanks a lot.

would really appreciate it if someone has a list of units they can share (mega, milli) and their conversions? thanks
I don't know if I have a good way of remember....

but I remember them because of computer memory kilobytes is 1000 bytes (or km is 1000m) mega is 106 giga 109 and you must have heard of tera- as well 1012.. but to be fair you probably won't come across that

milli is 10-3 (think of how many millimeters there are in a meter - 10 in 1cm & 100cm in 1m... therefore 1000mm in 1 meter)

micro is 10-6

nano is 10-9

Some calculators can convert units for you such as the fx--991ES, but I don't think you should have problems remember these powers

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