What does Lenz's law state about the direction of the induced current?

• A. It opposes the change in magnetic flux
• B. It enhances the change in magnetic flux
• C. It is perpendicular to the change in flux
• D. It has no relation to flux

Answer: (A)

When magnetic flux through a closed loop changes, an emf is induced in a direction that opposes that change. This opposition is built into Faraday’s law through the minus sign: emf = - dΦ/dt. So if the flux through the loop is increasing in a certain direction, the induced current creates a magnetic field in the opposite direction to oppose that increase; if the flux is decreasing, the induced current generates a field in the same direction as the original flux to help keep it from falling. You can determine the actual current direction by using the right-hand rule once you know whether the flux is rising or falling. The essential point is that the induced current always acts to oppose the change in magnetic flux.