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AQA Physics PHYA4 - Thursday 11th June 2015 [Exam Discussion Thread]

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Does anyone have a link for the specimen paper please?
Which EMF/flux linkage equations do we use and in which situations?
Original post by JackRowbotham
june 13 question 1.c) ... help?
also june 14 question 3 on the multiple choice?
pleasssssse:-)


any tips for the 6 marker?


Write everything you know? :lol:
Equation for electric potential in a uniform field?
Original post by RemainSilent
uhh i thought the closer = more KE the far more Ep ?

you're right i forgot the minus sign, the magnitude does decrease but due to the minus sign it just means its becoming less negative which is increasing
x
Reply 3805
Has Anyone got any tips for one of those 3 markers where you have to apply your knowledge... Whenever i come across them... I always get 1 or if i am lucky 2 marks... And sometimes no Marks.
Yeah my moneys on a SHM 6 marker
Does everyone reckon SHM for the 6 marker?
Original post by 000alex
Equation for electric potential in a uniform field?


V = q /(4*pi*epsilon*r)

It's in the data sheet. :smile:
Original post by lawson_g
Does everyone reckon SHM for the 6 marker?


I hope not. What would it be if it was about SHM? Like damping and stuff?
Original post by MsFahima
V = q /(4*pi*epsilon*r)

It's in the data sheet. :smile:


Isn't that only for a radial field?


Tried that equation for this question and it didn't work
Original post by JackRowbotham
june 13 question 1.c) ... help?
also june 14 question 3 on the multiple choice?
pleasssssse:-)


any tips for the 6 marker?


June 14 Q3: everything is in terms of seconds. Calculate the mass of water leaving per second using density formula (mass ÷ volume) as you know the volume and density. M works out to be 0.2 kg/s. Now to work out momentum you meed toe velocity of the water leaving per scond. You know the volume and the cross-area so use this to work out the length of water leaving per second which is equal to the speed ( volume ÷ area ) then the speed is 0.27. Mv is momentum so 0.27 x 0.2 = 0.055555 i.e 5.6×10^-2
Original post by ivyb
GPE inscreases (i.e. becomes less negative) since you have to put work in against the gravitational force (gains energy) to move it further from the planet. :smile:


Gpe does increase but does not become less negative, potential becomes less negatve the further away you go from a planet/body. This increase in gpe is equivalent to work done by an external force
Original post by Mehrdad jafari
Yeah I totally get the part where emf is max at 90 to field/flux lines as they are perpendicular and more are being cut.... But to me that is the same as maximum flux linkage as it's where the most flux is being cut!But I obviously can't see the difference between maximum flux linkage and maximum flux apart from the number of loops are considered!???!And maths explanations won't help I don't do alevel maths and didn't do GCSEs for years so Ihave only leant the basic physics maths skills


It's not really about whether you are doing maths or not. I'm doing a level maths too but i still haven't applied that maths anywhere in physics. The maths does help but that's where we have an idea of what's going on and not where we have no idea, lol


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Trust me if you try and start a physics A level not knowing ANY maths it makes a HUGE difference! It's full of maths... maybe what some would call 'basic' but I started not even knowing how to rearrange one equation!! And then there's exponentials, logs, the list goes on.... I've had to get a private maths tutor once a week just for the 'maths' part! But hopefully I'm mostly there now!
Original post by JackRowbotham
june 13 question 1.c) ... help?
also june 14 question 3 on the multiple choice?
pleasssssse:-)


any tips for the 6 marker?

And also question 1c. There is 2 ways of doing it dependent on which time period you use. I.e you can use the smaller time period (1.9) and divide this by theire difference (0.1) to get 19 swings until they are in phase. Then 19 swings times the period of the larger time period (2.0) equals 38 seconds. Or the other way is if you use the larger period initially (2.0) and divide this by their difference (0.1) to get 20 swings, then times this by the smaller time period (1.9) to again get 38 seconds
Original post by DannySmith420
June 14 Q3: everything is in terms of seconds. Calculate the mass of water leaving per second using density formula (mass ÷ volume) as you know the volume and density. M works out to be 0.2 kg/s. Now to work out momentum you meed toe velocity of the water leaving per scond. You know the volume and the cross-area so use this to work out the length of water leaving per second which is equal to the speed ( volume ÷ area ) then the speed is 0.27. Mv is momentum so 0.27 x 0.2 = 0.055555 i.e 5.6×10^-2


you're a star!
Original post by 000alex
Isn't that only for a radial field?


Tried that equation for this question and it didn't work


Potential is constant in a uniform field.
(edited 8 years ago)
How are the graphs related for induced emf and flux linkage?
Original post by MsFahima
E = V/D

And it's an electron so it will be attracted to the 50v plate.


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(edited 8 years ago)
Original post by donutellme
That's field strength...

Potential is constant in a uniform field

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oops. I understand what I've done wrong!

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