Lenz's Law provides the direction of the induced EMF: 'The direction of the induced EMF is such that it would tend to produce a current that opposes the change in magnetic flux that created it.'

• This is a consequence of the Law of Conservation of Energy.
• If the induced current supported the change, energy could be created out of nothing. The negative sign in Faraday's equation ($E=-d\Phi /dt$) reflects this law.