Second, because the magnetic field B and force are nonlinear functions of the current, depending on the nonlinear relation between B and H for the particular core material used. An electromagnet is a magnet that runs on electricity. This transformer was called a Sparker or Ignition coil, used to create the spark needed for the spark-plugs in cars from the '30s.
Transformers have a kVA rating which is the rated output Voltage times the rated output Amps divided by As can be visualized with the magnetic field lines, the magnetic field is strongest inside the magnetic material. Pretty amazing! It is made with a very fine small diameter wire, with only two layers.
The two photos on the right show how to demonstrate the transformer action using two coils and the AC electromagnet from our electromagnet experiments.
The effect of the core is to concentrate the field, and the magnetic field passes through the core more easily than it would pass through air. Jacob's Ladder using a neon sign transformer This Jacob's Ladder uses a transformer which creates 15,Vac on the secondary coil when Vac is applied to the primary coil.
As you vary the frequency and volume, the beads start to dance on the cone. When the volunteer is on the plank near the electromagnet, then disconnect the battery and watch the plate of the electromagnet pull away from the yolk of the electromagnet, causing the volunteer to drop about 1.
With four AA batteries, I know it can actually hold at least lbs. A common simplifying assumption satisfied by many electromagnets, which will be used in this section, is that the magnetic field strength B is constant around the magnetic circuit within the core and air gaps and zero outside it.