Consider Fig 11-1 The element dl moves at the velocity v The product dr da (v×dl)= dt dl=(dr×d)lt dt where da- drx di is the area swept by the element di over a small displacement dr
Thus V=frda d更 dt dt where gp is the magnetic flux passing through the closed path C, and d is its variance caused by the displacement dr The direction of y is determined as follows drives the current that generates a magnetic field in the opposite direction to the increase of the orig nal B The Faraday Law for vX B field