Magnets are the substances which have the property of attracting small pieces of iron, nickel, cobalt etc.,
This property of attraction is called magnetism. Magnetism is mediated by “magnetic field”.
Magnetic field is the region surrounding a magnet, in which the force of the magnet can be detected.
Magnetic field is a quantity that has both direction and magnitude. It is a vector quantity.
It is similar to an electric field surrounding a charge. A magnet attracts small pieces of iron even when they are at a certain distance away from it. This means that magnetic force acts at a distance like electric and gravitational forces. Magnetic field exists in the entire space surrounding the magnet.
Magnetic field is created by an electric current or magnetic dipole and the field imparts magnetic forces on other particles that are in it.
Interaction between magnet and magnetic field created by another that exerts a force on it.
Magnetic field is denoted by B.
MAGNETIC FIELD LINES/LINE OF FORCE
Magnetic field lines or lines of force are the imaginary lines to visualize magnetic field.
This was introduced by Michael Faraday.
For graphical representation of a field. If a magnet is placed on a cardboard and some iron fillings are sprinkled uniformly over it, the iron fillings are seen to arrange themselves in a pattern as shown. The iron fillings act as small magnets that experience force due to the magnetic field of the magnet.
The magnetic field lines always begin from the N-pole of a magnet and end on the S-pole of the magnet.
The magnetic field lines are the path along which an isolated unit north pole would move along in the field.
To plot the Magnetic Field Pattern due to a bar magnet by using a Compass, the magnetic field lines leave the north pole of a magnet and enter its south pole.
The strength of magnetic field is indicated by the degree of closeness of the field lines. So, magnetic field is the strongest, where the field lines are closest together.
PROPERTIES (OR CHARACTERISTICS) OF THE MAGNETIC FIELD LINES
These are closed and continuous curves which start in air from the N-pole and end at the S-pole and then return to the N-pole through the interior of the magnet.
The magnetic field lines come closer to one another near the poles of a magnet but they are widely separated at other places. So magnetic field lines are crowded near the pole where the field is strong and are far from the magnet where the field is weak. Parallel and equidistant magnetic field lines represent a uniform magnetic field, like the Earth’s magnetic field.
No two magnetic lines of force can intersect each other. If they intersect it would indicate two directions of magnetic field at that point which is not possible.