Similar to how an electric field surrounds a charge, we can consider a magnetic field and magnetic field lines to surround a magnet. We know that a magnet attracts small pieces of iron even when they are a certain distance away from it. Thus, the magnetic force, like electric force and gravitational force, acts at a distance. The idea of force acting at a `distance` can be easily understood by introducing the concept of field. We imagine a magnet as giving rise to a magnetic field, which exists, in the whole space surrounding it.
The phenomenon of magnetism is mediated by “magnetic field” – i-e, an electric current or magnetic dipole creates a magnetic field, and that field, in turn, imparts magnetic forces on other particles that are in the fields.
All materials are influenced by magnetic field to a greater or lesser degree.
The force that one magnet exerts on another can be described as the interaction between one magnet and the magnetic field of the other. A convenient method to describe magnetic field around a magnet is to draw magnetic field lines around it.
What are Magnetic Field Lines?
Magnetic field lines or lines of force are the imaginary lines introduced by Michael Faraday (1791-1867) to visualize magnetic field. Lines of force are graphical representation of a field. The lines of force are the path along which an isolated unit North Pole would move along in the field.
A simple experiment can be used to visualize the lines of force.
- Place a magnet on a cardboard and gently sprinkle some iron filings uniformly over it.
- The iron fillings are found to arrange themselves in a pattern as shown in the following figure.
- The reason these iron filings form the pattern is because each piece of iron filing becomes a small magnet and experiences a force in a certain distance in the magnetic field due to the magnet.
Properties of magnetic field lines:
- A magnetic field line is directed from north pole to south pole outside the magnet and from south pole to north pole inside the magnet.
- A magnetic field line is a closed and continuous curve.
- The magnetic field lines are crowded near the pole where the field is strong and far from the magnet where the field is weak.
- The magnetic field lines never intersect each other, otherwise if they do so there will be two direction of magnetic field at that point, which is absurd.
- In case the field lines are parallel and equidistant, they represent a uniform magnetic field. The Earth’s’ magnetic field is a uniform limited space.
So to summarize, the space surrounding a magnet in which magnetic force is exerted is called magnetic field. It is a vector quantity that has both direction and magnitude. The direction of magnetic field is taken by convention that the field lines emerge from North pole and merge at the South pole. The strength of a magnetic field can be observed from the degree of closeness of the field lines.
Learn more about magnetic fields and their behavior with our expert faculty here at BYJU’s.