High School Physics

Magnetic Field & Magnetic Field Lines

Last updated on October 11th, 2021 at 04:54 pm

This post defines the magnetic field and magnetic field lines. This also enlists the properties of magnetic field lines.

What is Magnetic field? | Define magnetic field

Magnetic Field & Magnetic Field Lines
Magnetic Field & Magnetic Field Lines

The space or area around a magnet in which its magnetic force can be felt is called a magnetic field. The magnetic field is a vector quantity i.e. it has both magnitude and direction.

In other words, A magnetic field is a region in space where a magnet or object made of magnetic material will experience a non-contact, magnetic force.

A moving charged particle has magnetic fields associated with it. One example of a charged particle that occurs in the most matter is the electron.

The direction of a magnetic field is taken to be the direction in which the north pole of the compass needle moves under the influence of the resultant force acting on it at a point in the magnetic field.

Define Magnetic field lines

When a small north magnetic pole is set free in the magnetic field of a magnet (say, a test magnet), it experiences some magnetic force and starts moving under the influence of the magnetic field of the test magnet. The path traced by a north magnetic pole around a magnet is called a magnetic field line of the magnet.

[Read about Magnetic field lines of permanent magnets & current-carrying wires.]

List the Properties of magnetic field lines

  • Magnetic field lines are closed curves. They emerge from the north pole and merge at the south pole of a bar magnet outside the magnet. Inside the magnet their direction is taken from south to north pole.
  • The magnetic field lines are crowded in the stronger magnetic field and are widely separated in the weaker magnetic field. In case of a bar magnet the magnetic field lines are closely packed near the poles indicating the strong magnetic field.
  • The direction of magnetic field at a point is given by the direction of tangent drawn at that point on the magnetic field line.
  • The magnetic field lines do not cross one another because if they do so then there will be two tangents at the point of intersection indicating two differnet directions of same magnetic field which is not possible.
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