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CBSE Class 12-science Answered

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Asked by arjunsah797 | 22 Mar, 2022, 07:03: PM
By Faraday's law of induction ,  Induced EMF E is given as

E = - dΦ/dt ...................(1)

where Φ is magnetic flux that is given as

Φ = ( B •A ) =  B A cosθ...........................(2)

where B is magnetic flux density , A is area of loop , θ is the angle between direction of magnetic field
and direction of normal to the loop area

From eqn.(1) and eqn.(2), we get

E = - A (dB/dt) cosθ  = - A ( dB/dt ) cos180 = A ( dB/dt) ....................(3)

From the direction of current flowing in the long wire , we get direction of magnetic field as going into the page as shown in figure.

By convention,  normal of the loop area is coming out of page.
Hence angle between direction of magnetic field and normal of loop area is 180o

Since magnetic field decreases rapidly , dB/dt is -ve , hence from eqn.(3) , induced EMF is negative.

If induced EMF is negative , then induced current also negative.

Negative induced current flows clockwise direction in loop as shown in figure.
Answered by Thiyagarajan K | 22 Mar, 2022, 08:47: PM

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