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

Reply 940

abro1089

2

Original post by particlestudent

Look at the two I quoted, everyone is saying different things :/.

this is from the textbook i am right. IMG_20160619_205537[1].jpg

Reply 941

particlestudent

13

Original post by TajwarC

How the hell does the formula work then?

Reply 942

Nerrad

7

Original post by particlestudent

Which one is right? :s-smilie:

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

Reply 943

abro1089

2

glad we cleared that up!

Reply 944

particlestudent

13

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! :smile:

Reply 945

boyyo

6

Is electric potential negative? (like gravitational potential)

Reply 946

Parallex

6

Original post by particlestudent

Which one is right? :s-smilie:

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.

(edited 7 years ago)

Reply 947

Nerrad

7

Yknow this physics thing is doing my head in

Reply 948

Nerrad

7

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

Reply 949

particlestudent

13

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

Reply 950

abro1089

2

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

Reply 951

TajwarC

17

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?

Reply 952

ememoville

8

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

Reply 953

aditisb1

1

Can someone please explain what back emf is?

Reply 954

boyyo

6

couple hours till the exam and I be getting baffed between emf and flux :s-smilie:

Reply 955

crashMATHS

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!

Reply 956

abro1089

2

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.