A simple Strong Electromagnet can be made by wrapping a coil of wire around a soft iron core.
We know that a straight current-carrying conductor produces a circular magnetic field around all points along its length, and that the direction of rotation of this magnetic field depends on the direction of current flowing through the conductor, left hand rule.
If we bend the conductor into a single loop, current will flow through the loop in opposite directions, creating a clockwise field and a counterclockwise field next to each other. The Strong Electromagnet uses this principle by magnetically linking several individual rings together to create a single coil.
A Strong Electromagnet is basically a coil that behaves like a rod magnet with distinct north and south poles when current is passed through the coil. The static magnetic field produced by each individual coil loop adds to its adjacent magnetic field, and the combined magnetic field is concentrated, just like the single wire loop we saw in the last tutorial in the center of the coil. The resulting static magnetic field is uniform with a north pole at one end and a south pole at the other end, and the center of the coil is much stronger than the periphery.
We now know that two adjacent conductors are carrying current and the magnetic field is set according to the direction of the current. The resulting interaction of the two fields subjects the two conductors to mechanical forces.
When the current flows in the same direction (same side of the coil), the field between the two conductors is as shown above, it is weak and there is an attractive force. Likewise, when currents flow in opposite directions, the magnetic field between them becomes stronger and the conductors are repelled.
The field strength around a conductor is proportional to its distance, with the strongest point being the next to the conductor and gradually getting farther and farther away from the conductor. In the case of a single straight conductor, the current flowing and the distance from it are the factors that determine the strength of the magnetic field.
The magnetic field strength of a Strong Electromagnet also depends on the type of core material, which is used as the core primarily to focus the magnetic flux in a well-defined and predictable path. So far, only air-core (air-core) coils have been considered, but introducing other materials into the core (center of the coil) has a great control over the magnetic field strength.