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# Trasnformers watch

1. ok I just want to make sure of the graphs of the fluxlinkage and the emf and the current..so anybody knows alinbk that explain it more with the graphs I really need it
2. habosh were did u revise this topic off...wat book that is?
3. flux linkage against emf should be a straight line through the origin with constant gradient (faradays law)
flux linkage against current when flux linkage is positive, current is negative...
(lenz's law)
4. generally like 85% of the time its 90deg out
5. (Original post by mackin boi)
habosh were did u revise this topic off...wat book that is?
our beloved nelson book
6. (Original post by El Chueco)
flux linkage against emf should be a straight line through the origin with constant gradient (faradays law)
flux linkage against current when flux linkage is positive, current is negative...
(lenz's law)
the current is not a dc in transformer so it will be a sinosoidal but I just wanna make sure so they values keep changing going minimum when magnetic flux is max ..etc...
7. (Original post by habosh)
our beloved nelson book

cud u tell me wat page
8. e = - dΦ/dt

so if they give you a graph of the emf against time, just take the gradients at different points. So if it is sinusoidal (sp), around t = 0, there is a positive max gradient for the emf, so the flux is going to be maximum at this time. But since the emf is proportional to minus dΦ/dt, it will be a minimum turning point.

I think the examiner will give you the marks anyway if you draw them at π/2 phase difference anyway.
9. thanx the current is in phase and the voltage or emf is pi/2
10. (Original post by habosh)
thanx the current is in phase and the voltage or emf is pi/2
i dont know about the current . Can you explain why it is in phase?
11. (Original post by Mathemagician)
i dont know about the current . Can you explain why it is in phase?
well I'm actully not sure about that though..but I remember that it's exaclty the same shape. I'm not sure thats why I asked this
12. this is all new 2 me...current in phase...turning points on emf grafs...im buggered..habosh wat page is this all on????
13. (Original post by mackin boi)
this is all new 2 me...current in phase...turning points on emf grafs...im buggered..habosh wat page is this all on????
the one about transformers in the magnetism section my room is a mess and I can't find my bok I left it somewhere around the house
14. (Original post by habosh)
well I'm actully not sure about that though..but I remember that it's exaclty the same shape. I'm not sure thats why I asked this
emf is proportional to the current. Thats why they produce the same shape?
15. (Original post by mackin boi)
this is all new 2 me...current in phase...turning points on emf grafs...im buggered..habosh wat page is this all on????
Whats a turning point?!

Can someone draw these graphs quickly in paint
16. (Original post by SinghFello)
Whats a turning point?!

Can someone draw these graphs quickly in paint
a turning point is when the line turns . sorry, had to say that .

it is like the end of the 'bucket' of a y = x^2 graph. So for the sine graph, it goes from the maximum value (turning point) of 1 to the minimum (turning point) of -1 [only if its y = sin nx]
17. So can someone summarise this thread

All plotted against time:

emf pi out of phase with flux
because of lenzs law

and if flux is plotted against emf/current, its a straight line with positive gradient

is this right?
18. (Original post by SinghFello)
So can someone summarise this thread

All plotted against time:

emf pi out of phase with flux
because of lenzs law
emf is pi/2 out of phase with flux.
19. (Original post by Mathemagician)
emf is pi/2 out of phase with flux.
Math can u draws up these grafs pleeez
20. Okay...
Vout = - n2dΦ/dt
Iin n1 = Φ

That all that is known for sure. The phase of Vin relative to Iin is dependant on the coil and the power supply. The phase of Vout relative to Iout is dependant on the secondary coil and the load(s). However for the most parts, I don't believe you need to know this for ALevel Physics. If you did need to know you would probabily know a wee bit about complex impediance [Z = V/I].
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