ELECTROMAGNETIC FIELDS:

Electricity and magnetism are two separate but closely related forces. This is demonstrated by the fact that magnetic lines of force are produced around magnets, and also around conductors carrying electrical current. When electrical current is passed through a conductor, there will always be a magnetic field surrounding the conductor. The strength of this magnetic field depends upon the amount of current flow. The higher the amperage, the greater the magnetic strength.

If two conductors are arranged side by side and current passes through both conductors in the same direction, the magnetic field around each conductor will be in the same direction. As a result, the magnetic fields will combine to form one stronger field surrounding both conductors. This causes the two conductors to be drawn together or attracted to each other. If the current is in opposite direction, the magnetic fields surrounding the two conductors will oppose each other and result in a repelling action. This is the principle involved in the operation of an electric motor such as a starter motor on a vehicle.

If a conductor is wound into a coil, the current passing through it will flow in the same direction in all turns. The magnetic field produced by each turn combines with the field produced by adjacent turns, resulting in a strong continuous field lengthwise around and through the coil. The polarity of the field produced by the coil depends upon the direction of current flow, and the direction in which the coil is wound. The strength of the magnetic field depends upon the number of wire loops and the amount of current passed through the coil. This is known as AMPERE TURNS.

The strength of the magnetic field around the coil can be materially strengthened by placing a core of soft iron inside the coil. Because the iron is a much better conductor for the magnetic lines of force than is the air, the field becomes more concentrated and much stronger. Electromagnetic relays using this basic design are used in many applications in the electrical system of the automobile.

ELECTROMAGNETIC FIELDS