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# AQA Physics PHYA4 - 20th June 2016 [Exam Discussion Thread] watch

1. In the emf induced in a rotating coil equation, what is the w (omega i thing) Is it just angular velocity?
2. (Original post by boyyo)
for this question, would you use left or right hand rule
Left hand; current into page, field to the right, force down.
3. (Original post by abro1089)
i think its important to realise that at the point where the SIDES of the coil are parallel to the field lines, the PLANE of the coil is perpendicular. and vice versa.
yup. glad we cleared that one up
4. In the emf induced in a rotating coil equation, what is the w (omega i thing) Is it just angular velocity? Also does anyone have any ideas on what the 6 marker could be?
5. (Original post by McDerdactyl)
In the emf induced in a rotating coil equation, what is the w (omega i thing) Is it just angular velocity?
Yes.
6. What is the phase difference between acceleration and displacement of an object in SHM? pi?
7. (Original post by boyyo)
for this question, would you use left or right hand rule
Both and start shouting "POW POW POW" automatically get full marks

Left hand rule btw
8. (Original post by ombtom)
Yes.
Thanks I feel so stupid atm everything has left my brain
The RATE of change of flux linkage is max when the coils are parallel with the field lines
But i thought EMf = rate of change of flux linkage, therfore shouldnt emf induced be max
10. (Original post by jonnypiercy)
Shout out to Tom Muir 😂😂
Bro! I heard if you don't answer any of section A they presume there was a scanning error and give you full marks!!
11. (Original post by boyyo)
for this question, would you use left or right hand rule
You would use left hand rule as the right hand rule is for generators.

12. (Original post by C0balt)
What is the phase difference between acceleration and displacement of an object in SHM? pi?
Yeah, or 180 degrees.
13. (Original post by C0balt)
What is the phase difference between acceleration and displacement of an object in SHM? pi?
Yeah.

I just remember it by every differential it goes up by pi/2 (the phase difference)
14. (Original post by Muirrrr)
Bro! I heard if you don't answer any of section A they presume there was a scanning error and give you full marks!!
Sounds legit!!!!
15. (Original post by ombtom)
Yeah, or 180 degrees.
(Original post by particlestudent)
Yeah.

I just remember it by every differential it goes up by pi/2 (the phase difference)
yeee cheers
16. (Original post by boyyo)
for this question, would you use left or right hand rule
Left. Always use left unless it is a generator
17. This is why I don't check TSR before exams, trying to not let myself undo all my revision by confusing myself with all your different theories
18. (Original post by Muirrrr)
Bro! I heard if you don't answer any of section A they presume there was a scanning error and give you full marks!!
God I wish
19. Why does the graph of potential energy in 2014 show a vertically oscillating Spring mass system as having 0 potential energy at some points? Surely at the equilibrium it has gravitational potential energy and at the bottom elastic?
20. (Original post by particlestudent)
Look at the two I quoted, everyone is saying different things :/.
the induced EMF is directly proportional to the rate of change of flux linkage, the rate of change of flux cut is greatest when the coil is parallel to the field

When the coil is perpendicular to the magnetic field the rate of change of flux cut is zero, but the flux linkage is at a maximum. You can see this graphically by looking at the gradient of a flux linkage graph

I remember it by thinking of it in terms of a differential, it's pretty confusing initially

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