Lenz’s law states that the polarity of the induced emf is such that it
tends to produce a current which opposes the change in magnetic flux
that produces it The negative sign in the expression for Faraday’s law
indicates this fact 4 When a metal rod of length l is placed normal to a uniform magnetic
field B and moved with a velocity v perpendicular to the field, the
induced emf (called motional emf) across its ends is
e = Bl v
5