NEET Questions Solved


A uniform but time-varying magnetic field B(t) exists in a circular region of radius a and is directed into the plane of the paper, as shown. The magnitude of the induced electric field at point P at a distance r from the centre of the circular region 

(1) Is zero

(2) Decreases as 1r

(3) Increases as r

(4) Decreases as 1r2

(2) Construct a concentric circle of radius r. The induced electric field (E) at any point on the circle is equal to that at P. For this circle

E.dl=dϕdt=AdBdt 

or E×(2πr)=πa2.dBdt

E=a22rdBdtE1r 

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