ATAR Notes: Forum

HSC Stuff => HSC Science Stuff => HSC Subjects + Help => HSC Physics => Topic started by: Jefferson on October 03, 2019, 07:21:02 pm

Title: Induced EMF in Coil
Post by: Jefferson on October 03, 2019, 07:21:02 pm

Does anyone know how to solve?

The source answer is A, people debating over B (because half a revolution produces 12V, then another half produced 12V to make 24V).

Title: Re: Induced EMF in Coil
Post by: THSCStudyOnly on October 03, 2019, 07:51:14 pm

I might be wrong here, but doesn't it produce 12V per one whole rotation?
Here is my reasoning:

emf = -N(d(Φ)/dt)
       = (-200(0.05 x 0.16²)) / (1/46.8 )
       = -11.98V
       = (approx) 12V

And since I used 1/46.8 it should be one rotation produces 12V (because it takes 1/46.8s for it to spin one rotation)

Title: Re: Induced EMF in Coil
Post by: Jefferson on October 04, 2019, 03:45:22 pm

Quote from: THSCStudyOnly on October 03, 2019, 07:51:14 pm

I might be wrong here, but doesn't it produce 12V per one whole rotation?
Here is my reasoning:

emf = -N(d(Φ)/dt)
       = (-200(0.05 x 0.16²)) / (1/46.8 )
       = -11.98V
       = (approx) 12V

And since I used 1/46.8 it should be one rotation produces 12V (because it takes 1/46.8s for it to spin one rotation)

Sure, but the change in flux for half a rotation is
0.05 * 0.16^2. This is because it goes from 0 degrees to 180 degrees.
So for a full rotation, it should be 2 * 0.05 * 0.16^2

That's where the 24 is coming from.