Electrical Revision

When two N poles or two S poles of a magnet are together the magnetic flux lines are pushed outwards away from each other. When a N and a S pole are placed together the magnetic flux lines are straight and are attracted to each other.

The amount of lines of flux in any particular area is called the flux density. The lines of flux appear to go through the North pole of the magnet round the outside and enter into the South pole. If the lines of flux were close together you would have a strong magnetic field. If they were further apart then the magnetic field is weak.

The amount of lines of flux in a particular area is called magnetic flux density.

Flux; Symbol F (phi), Unit Weber (Wb)
Flux density; Symbol B, Unit Tesla (T) or (Wb/m2)

When a conductor carries a current, a magnetic field forms around it. The magnetic field is circular and extends along the length of the conductor. You can determine the direction of the magnetic field using the RIGHT HAND GRASP RULE.

A magnetic field will increate within a solenoid, a solenoid occurs when the conductor is formed into a series of turns with nothing in them but air. If the turns of wire are wound around a core it is termed as a coil. If each turn of the coil is a conductor, then increasing the number of turns increases strength of the magnetic field.

More turns = Increased Magnetic Field Strength.

To determine the direction of the magnetic field in a solenoid assume that the fingers on the right hand are showing the direction of current in the coil or solenoid and that the thumb is pointing north as shown in the picture above..