- Coil of wire around an iron core - An electrodynamic spiral having the conjuctive wire
turned back along its axis, so as to neutralize that component of the
effect of the current which is due to the length of the spiral, and
reduce the whole effect to that of a series of equal and parallel
circular currents. When traversed by a current the solenoid exhibits
polarity and attraction or repulsion, like a magnet.