Faraday's Law Video Lessons

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# Problem: Induced EMF and Current in a Shrinking LoopShrinking Loop. A circular loop of flexible iron wire has an initial circumference of 161cm , but its circumference is decreasing at a constant rate of 13.0cm/s due to a tangential pull on the wire. The loop is in a constant uniform magnetic field of magnitude 1.00T , which is oriented perpendicular to the plane of the loop. Assume that you are facing the loop and that the magnetic field points into the loop.Find the magnitude of the emf EMF induced in the loop after exactly time 8.00s has passed since the circumference of the loop started to decrease.

###### FREE Expert Solution

Induced emf:

$\overline{){\mathbf{\epsilon }}{\mathbf{=}}{\mathbf{-}}\frac{\mathbf{d}{\mathbf{\varphi }}_{\mathbf{B}}}{\mathbf{d}\mathbf{t}}}$

Magnetic flux:

$\overline{){{\mathbf{\varphi }}}_{{\mathbf{B}}}{\mathbf{=}}{\mathbf{B}}{\mathbf{A}}{\mathbf{c}}{\mathbf{o}}{\mathbf{s}}{\mathbf{\theta }}}$

The magnetic field is parallel to the normal of the loop's area.

Therefore, θ = 0

We are also told that (dC/dt) = -13cm/s(1m/100cm) = -0.13 m/s

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###### Problem Details

Induced EMF and Current in a Shrinking Loop
Shrinking Loop. A circular loop of flexible iron wire has an initial circumference of 161cm , but its circumference is decreasing at a constant rate of 13.0cm/s due to a tangential pull on the wire. The loop is in a constant uniform magnetic field of magnitude 1.00T , which is oriented perpendicular to the plane of the loop. Assume that you are facing the loop and that the magnetic field points into the loop.

Find the magnitude of the emf EMF induced in the loop after exactly time 8.00s has passed since the circumference of the loop started to decrease.