27. A rectangular, a square, a circular and an elliptical loop, all in the (x-y) plane, are moving out of a uniform magnetic field with a constant velocity, $\vec{v} = v\hat{i}$. The magnetic field is directed along the negative z axis direction. The induced emf, during the passage of these loops, out of the field region, will not remain constant for: (2009)
Solution:
The magnitude of induced emf is $e = B l_{eff} v$, where $l_{eff}$ is the length of the conductor cutting the field lines.
For rectangular and square loops, $l_{eff}$ is constant as they exit the field, resulting in a constant emf.
For circular and elliptical loops, $l_{eff}$ continuously varies with time, so the induced emf does not remain constant.
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