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# Transformers watch

1. http://filestore.aqa.org.uk/subjects...1-QP-JUN12.PDF

Could someone pls explain why the answer to question 24 is C ??
2. (Original post by HG1)
http://filestore.aqa.org.uk/subjects...1-QP-JUN12.PDF

Could someone pls explain why the answer to question 24 is C ??
That's when the fastest change in magnetic flux is.
3. (Original post by morgan8002)
That's when the fastest change in magnetic flux is.
Ah thanks mate , would you mind explaining in more detail ? Sorry my understanding is lacking
4. (Original post by HG1)
Ah thanks mate , would you mind explaining in more detail ? Sorry my understanding is lacking
The magnitude of the induced emf is equal to the magnitude of the rate of change of magnetic flux in the second coil. By Ohm's law this is proportional to the induced current. So the magnitude of the induced current is proportional to the magnitude of the rate of change of the magnetic flux across the second coil.

On the other hand, the magnetic flux across the second coil is proportional to the magnetic flux density, which is proportional to the current through the first coil.

So the magnitude of the induced current in the second coil is proportional to the magnitude of the rate of change of the current though the first coil.

The current in the first coil only increases slowly, so the greatest magnitude of the rate of change of the current in the first coil is when the switch is opened and the current suddenly drops to 0.
5. [QUOTE=morgan8002;64122995]The magnitude of the induced emf is equal to the magnitude of the rate of change of magnetic flux in the second coil. By Ohm's law this is proportional to the induced current. So the magnitude of the induced current is proportional to the magnitude of the rate of change of the magnetic flux across the second coil.

On the other hand, the magnetic flux across the second coil is proportional to the magnetic flux density, which is proportional to the current through the first coil.

So the magnitude of the induced current in the second coil is proportional to the magnitude of the rate of change of the current though the first coil.

The current in the first coil only increases slowly, so the greatest magnitude of the rate of change of the current in the first coil is when the switch is opened and the current suddenly drops to 0.[/QUOTE

Thank you so much ! It's so much more clear now
6. (Original post by HG1)

Thank you so much ! It's so much more clear now
No problem.

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