- #1

BrandonInFlorida

- 54

- 24

- Homework Statement
- This is a section of my book I don't understand, not literally homework. They (Halliday and Resnick) show a circular region containing a homogeneous magnetic field, which is increasing in strength. They then consider concentric circles within the region.

Faraday's Law states that the induced EMF around each loop is the negative of the time rate of change of the flux. They show how larger and larger circles within the circular region have larger and larger fluxes, more importantly larger and larger time rates of change of flux and, therefore, larger induced EMFs.

I'm with them so far. What I don't understand is when they say that concentric circles outside the region have zero induced EMF. It seems to me that once the circle considered becomes larger than the circular region containing the field, the flux and its time derivative remain constant for bigger and bigger circles. It doesn't fall to zero, so the induced EMF wouldn't fall to zero, according to Faraday's Law.

- Relevant Equations
- EMF = derivative of flux with respect to time

Can anyone show me where I'm wrong?