Magnetic Field And Magnetic Field Lines

Similar to how an electric field surrounds an electric charge, the magnetic field is the area around a magnet which exert a magnetic force and it is a result of moving electric charges. Magnetic field lines are a visual tool used to represent magnetic fields. The direction of the field is shown by the direction of the magnetic flux lines at all times, at all places.


What is a Magnetic Field?

The magnetic field can be defined as:

“A region around/surrounded by a moving electric charge or a magnetic material within which the force of magnetism acts.”

Symbol B or H
Unit Telsas
Base unit (Newton.Second)/Coulomb

We can consider a magnetic field surrounding 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 a 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.

 

Magnetic Field

Magnetic Field

Figure: A pictorial representation of the magnetic field. Which describes how a magnetic force is distributed within and around a magnetic material.

Well, most of us know something about magnetic objects. Rather we might have experienced that there is some force acting between them. Basically, 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 this force 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 the magnetic field around a magnet is to draw field lines around it.

How does Magnetic Field occur?

If you are wondering how Magnetic fields occur. Well, it occurs whenever a charge is in motion. That being said if you apply more charge in the motion the strength of a magnetic field usually increases. Besides, Magnetism and magnetic fields are part of the electromagnetic force which is indeed one of the four prime forces of nature.

How is Magnetic Field illustrated?

Typically, a magnetic field can be illustrated in two different ways.

  • Magnetic Field Vector
  • Magnetic Field Lines

Magnetic Field Vector:

Mathematically, it can be described as a vector field. The vector field can be marked directly as a set of many vectors which can be drawn on a grid. In this case, the vector points that are pointing in the direction of the compass has the length dependent on the strength of the magnetic force.

All in all, it simply means the magnetic field is a vector quantity that has both direction and magnitude.

Magnetic Field Vector

Magnetic Field Representation

There are two different vectors that are usually used to represent the magnetic field.

  • The magnetic induction or magnetic flux density which is symbolized by B
  • The magnetic field intensity or magnetic field strength. It is symbolized by letter H.

What are Magnetic Field Lines?

Apart from vectors, it can be represented with the use of field lines. Magnetic field lines are nothing but imaginary lines. Here, the density of the lines indicates the magnitude of the field. Taking an instance, the magnetic field is stronger and crowded near to the poles of a magnet. As we move away from the poles it will be weak and we can see by the lines, they become less dense.

 

Magnetic Field Lines

Magnetic Field Lines

 

What are Electromagnetic Waves?

Thus, we got to know the electric field and magnetic field are interdependent in a few cases. This mechanism can be applied to explain the propagation of waves like radio waves, x-ray, Infrared, visible, gamma waves, ultraviolet waves etc. In short, these are the radiations or waves which we categorise under the banner of electromagnetic waves.

So, what are electromagnetic waves? the waves that are propagated by simultaneous periodic variations of electric and magnetic field intensity is called electromagnetic waves.

Practice Questions & FAQs

Q1: Explain magnetic field.

Ans: It is a region surrounded by a moving electric charge or a magnetic material within which the force of magnetism acts.

Q2: Explain magnetic field lines.

Ans: They are a visual tool used to represent magnetic fields.

Q3: Why the direction of the magnetic flux lines is important?

Ans: The direction is shown by the direction of the magnetic flux lines.

Q4: Write SI unit of magnetic field

Ans: The SI unit is Telsa(T)

Q5: Write the formula for the magnetic field of a straight current carrying wire and explain the terms.

Ans: \(B=\frac{\mu _{0}I}{2\pi d}\)

Here, B is the strength of the magnetic field at distance d.
I is the current flowing through a wire
\(\mu _{0}\) is the permittivity of free space

Q6: Write some magnetic field examples.

Ans: Some example are: motor, compass.

Q7: Name the device which holds magnets

Ans: Refrigerator, Railway lines, rollercoasters, Speakers etc.

Q8: How the magnetic field can be artificially generated?
Ans: It can be artificially generated varying electric field.

Q9: What are electromagnetic waves?

Ans: The waves that are propagated by simultaneous periodic variations of electric and magnetic field intensity is called electromagnetic waves.

Q10: Name two different vectors representation the magnetic field.
Ans: The two different vectors representation is:

  • The magnetic induction or magnetic flux density which is symbolized by B.
  • The magnetic field intensity or strength. It is symbolized by letter H.

Practise This Question

At which of the following locations is a magnetic compass functional?