Magnetic Field:

Magnetic Field: Region in space around a magnet where the magnet has its magnetic effect is called magnetic field of the magnet.

Intensity of magnetic field or magnetic flux density: magnetic flux density of a point in a magnetic field is the force experienced by a north pole of unit strength placed at that point. Its SI unit is Newton/ ampere-meter or Weber/ meter² or tesla (T) 

Magnetic lines of force: The magnetic lines of force are imaginary curves which represent a magnetic field graphically. The tangent drawn at any point on the magnetic liens of force gives the direction of magnetic field at that point.

Properties of magnetic liens of force:

(i)                  Magnetic lines of force are closed curves. Outside the magnet they are form north to South Pole and inside the magnet they are from south to North Pole.

(ii)                Two lines of force near intersect each other.

(iii)               If the lines of force are crowded, the field is strong.

(iv)              If the liens of force are parallel and equidistant, the field is uniform.

Magnetic Substance: On the basis of magnetic behavior, substances can be divided into three categories.

(i)          Diamagnetic substance: Diamagnetic substances are such substances which when placed in a magnetic field; acquire feeble magnetism opposite to the direction of magnetic field.

        Examples: Bismuth, Zinc, Copper, Silver, Gold, Diamond, Water, Mercury, Water etc.

(ii)        Paramagnetic Substance: Paramagnetic substances are such substances which when placed in a magnetic field acquire a feeble magnetism in the direction of the field.

       Examples: Aluminum, Platinum, Manganese, Sodium, Oxygen etc.

(iii)          Ferromagnetic substance: Ferromagnetic substances are those substance, which when placed in a magnetic field, are strongly magnetized in the direction of field.

Example: Iron, Cobalt, Nickel etc.