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

1. (Original post by particlestudent)
Look at the two I quoted, everyone is saying different things :/.
this is from the textbook i am right.
2. How the hell does the formula work then?
3. (Original post by particlestudent)
Which one is right?
I am. I just realised i got mistaken. Anyway what i meant to say was emf is max when the flux linkage for the coil is zero, ignore anything I said about the field lines
4. glad we cleared that up!
5. (Original post by kingaaran)
The alternating current generator:

You have the greatest emf induced when the sides of your coil are perpendicular to the field lines. This is where the rate of change of flux linkage is largest, generating the maximum emf.

You have the smallest emf when the sides of your coil are parallel to the field lines. This is where the rate of change of flux linkage is least, generating the lowest emf (which is, in fact, 0).

People on here seem to be getting confused between the sides of the coil and the plane of the coil.
Thank you!
6. Is electric potential negative? (like gravitational potential)
7. (Original post by particlestudent)
Which one is right?
Nerrad is right. If you think of a coil where the plane of the coil is perpendicular to the magnetic flux, there is maximum flux associated with the coil so the flux linkage is MAXIMUM. A slight rotation of the coil won't change the amount of flux associated with the coil, so the rate of change of flux linkage is small. EMF is proportional to the rate of change of flux linkage (Faraday's Law), so the induced EMF is minimum when the plane of the coil is perpendicular to the field.

If the plane of the coil is parallel to the field, the magnetic flux associated with the coil is 0. A slight rotation of the coil will associate flux with the coil so the rate of change of flux linkage is higher as it begins at 0 flux linkage when parallel. EMF is maximum when the coil is rotated from a position parallel to magnetic flux.
8. Yknow this physics thing is doing my head in
9. Guys you've left me in an existential situation where I don't even know what's right or wrong anymore. I guess I'm gonna go off this forum for a bit now. Ciao. Hope you guys figure it out
10. (Original post by Parallex)
Nerrad is right. If you think of a coil where the plane of the coil is perpendicular to the magnetic flux, there is maximum flux associated with the coil so the flux linkage is MAXIMUM. A slight rotation of the coil won't change the amount of flux associated with the coil, so the rate of change of flux linkage is small. EMF is proportional to the rate of change of flux linkage (Faraday's Law), so the induced EMF is minimum when the plane of the coil is perpendicular to the field.

If the plane of the coil is parallel to the field, the magnetic flux associated with the coil is 0. A slight rotation of the coil will associate flux with the coil so the rate of change of flux linkage is higher as it begins at 0 flux linkage when parallel. EMF is maximum when the coil is rotated from a position parallel to magnetic flux.
This has confused me even more. I think Kingaran cleared it up at the top as to why everyone keeps saying different things
11. (Original post by Parallex)
Nerrad is right. If you think of a coil where the plane of the coil is perpendicular to the magnetic flux, there is maximum flux associated with the coil so the flux linkage is MAXIMUM. A slight rotation of the coil won't change the amount of flux associated with the coil, so the rate of change of flux linkage is small. EMF is proportional to the rate of change of flux linkage (Faraday's Law), so the induced EMF is minimum when the plane of the coil is perpendicular to the field.

If the plane of the coil is parallel to the field, the magnetic flux associated with the coil is 0. A slight rotation of the coil will associate flux with the coil so the rate of change of flux linkage is very high as it begins at 0 flux linkage when parallel. EMF is maximum when the coil is rotated from a position parallel to the field.
quoting from the textbook says: the induced emf is zero when the sides of the coil move parallel to the field lines
12. (Original post by kingaaran)
The alternating current generator:

You have the greatest emf induced when the sides of your coil are perpendicular to the field lines. This is where the rate of change of flux linkage is largest, generating the maximum emf.

You have the smallest emf when the sides of your coil are parallel to the field lines. This is where the rate of change of flux linkage is least, generating the lowest emf (which is, in fact, 0).

People on here seem to be getting confused between the sides of the coil and the plane of the coil.
okay this clear it up nicely. The plane is essentially when you look at it from above, right?
13. (Original post by kingaaran)
I'm guessing a 6 marker on SHM is due... Probably something to do with damping / resonance or a calculation based one
What could you say for 6 marks on SHM? and Damping was done a lot last year
14. Can someone please explain what back emf is?
15. couple hours till the exam and I be getting baffed between emf and flux
16. (Original post by TajwarC)
okay this clear it up nicely. The plane is essentially when you look at it from above, right?
Yeah

(Original post by ememoville)
What could you say for 6 marks on SHM? and Damping was done a lot last year
Depends on whatever they want to question you on!
17. 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.
18. I think the 6 marker will most likely be -

Transformers
Electromag situation
Cycletron
19. for this question, would you use left or right hand rule
Attached Images

20. Shout out to Tom Muir 😂😂

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