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## Homework Statement

A wire loop of radius 0.3m lies so that an external magnetic field of magnitude 0.30 T is perpendicular to the loop. The field reverses its direction, and its magnitude changes to 0.20 T in 1.5s. Find the magnitude of the average induced emf in the loop during this time.

## Homework Equations

[tex] \varepsilon_{avg} = \frac{-\Delta \Phi_{B}}{\Delta t}[/tex]

[tex]\Phi_{B}=BAcos \theta [/tex]

## The Attempt at a Solution

[tex]A=\pi r^{2}=\pi (0.30m)^{2}= 0.09\pim^{2}[/tex]

[tex]0s: \Phi_{B}=BA cos \theta =(0.30T)(0.09\pi m^{2}) = 0.0848 T*m^{2}[/tex]

[tex]1.5s: \Phi = -(0.20T)(0.09\pi m^{2})= -0.05655 T*m^{2}[/tex]

[tex]\varepsilon_{avg}=\frac{(-0.05655-0.0848)}{1.5s}=-0.14135[/tex]

The correct answer, however, is 94 mV??

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