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# The cross-sectional area of an adjustable single loop is reduced from 1.2 m^2 to 0.40...

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The cross-sectional area of an adjustable single loop is reduced from 1.2 m^2 to 0.40 m^2 in 0.25 seconds.  What is the average emf that is induced in this coil if it is in a region where B = 1.5 T downward, and the coil's plane is perpendicular to B?

Posted by lkehoe on April 15, 2013 at 6:32 PM via web and tagged with area, coil, cross-sectional, emf, perpendicular, physics, reduced, science, seconds, single loop

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magnetic flux

`phi=BA`

Thus magnetic flux when area of cross section  1.2 sq m is

`phi= 1.5xx1.2 ` Wb

`phi=1.8 Wb`

The magnetic flux ,when area of cross section .4 sq m is

`phi_1=1.5xx.4 Wb`

`=.6 Wb`

`Delta phi`

`Delta phi=.6-1.8`

`=-.12 Wb`

`Time=Deltat`

`Deltat=.25`

emf= `(Deltaphi)/(deltat)`

`=-1.2/.25`

`=-4.8V`

Posted by pramodpandey on April 16, 2013 at 5:51 AM (Answer #1)

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