English: Diagram of eddy currents (I, red) induced in conductive metal sheet (C) moving under a stationary magnet (N), showing the origin of the braking force The magnetic field lines (B, green) from the North pole of the magnet extend down through the sheet. The increasing field at the leading edge of the magnet (left) causes the currents to circle counterclockwise. Thus from Lenz's law they create their own magnetic field directed up (left blue arrow) which opposes the magnet's field, thus exerting a drag effect on the magnet. Similarly, at the trailing edge of the magnet (right) the decreasing magnetic field induces eddy currents that circle clockwise. This creates a magnetic field directed down (right blue arrow) which attracts the magnet, which also exerts a retarding force on the magnet.