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                                    A conducting circular loop is expanding in a magnetic field of 2T uniformly so that rate of increase of its radius R is 1 cm/s. Find the induced emf in the loop when its radius is 20 cm. The field is perpendicular to the plane of the loop. | 
                            
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Answer»  `0.2pixx10^(-2)` V `phi=AB=pir^2B` `THEREFORE epsilon=-(dphi)/(DT)` `=-d/(dt)[pir^2B]` `=-piB.(d(r)^2)/(dt)` `=-2piBr. (DR)/(dt)` `therefore |epsilon|=2pixx2xx0.2xx0.01` `=8pixx10^(-3)` V `therefore |epsilon|=0.8pixx10^(-2)` V  | 
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