Suppose there is an object with a permanent magnet attached to it that can slide on a linear track. The object is initially at rest and the permanent magnet alligns with the axis of an electro-magnet. If the electro-magnet is pulsed on momentarily with a current so that the object acquires a kinetic energy equal to 1 joule, typically how much electrical energy would be needed for the object to acquire this kinetic energy? I assume it would take more that 1 joule of electrical energy to impart 1 joule of kinetic energy to the object. But how much? What would be the theoritical maximum efficieny of the electro-magnetic pulser?