- #1

teroenza

- 195

- 5

## Homework Statement

I have been asked to calculate the magnitude of the induced electric field using Faraday's law. I am unable to provide the picture that accompanies the problem and must describe it with words.

A circle has a magnetic field (perpendicular to the circle) directed into the page throughout it, that varies with time. This circle has a radius R. I am asked to calculate the E field strength at a point outside this circle, located at a distance 2R from the center of the original circle. There is no field outside the circle (past distance R).

I have seen the solution to the problem and Faraday's law is used to solve it. For the line integral they use the circle's radius

Line integral becomes E*2pi*R

But for the surface integral (to get flux) they use the distance to the point (2R).

negative change in flux becomes -(d/dt) (B*pi*(

**2R**)^2)

Can someone please help me. I thought that for Faraday's law, the line integral should be bounding the surface.

## Homework Equations

EMF=−N ΔΦBΔt or −N dΦBdt
Last edited: