If we bring a bar magnet near to another bar magnet then a force acts between the magnets. Same poles of magnets repel and opposite poles attract each other. This interaction is similar to electric charges. Now what makes this to happen? The answer is the magnetic force in the magnetic field. We already know that an electric charge can produce an electric field around it and interacts with other charges in that region. Similar things also happen in the magnetic field. In this article, we are going to discuss the origin and definition of magnetic field, unit, dimension and properties of magnetic field.
Contents in this article:
- Origin of magnetic field
- Definition of magnetic field intensity
- Properties of Magnetic field
- Unit of magnetic field
- Dimension of magnetic field
- Definition of 1 Tesla
- Uniform Magnetic field
Origin of Magnetic field
The first magnet was found in the Magnesia region of Asia. It was in the form of a stone of Ferric Oxide (Fe2O3 ). Some scientist said that the magnet formed due to the strikes of lightning on the asteroids. Then we got those asteroid stones when those fall on the earth. But the exact cause of formation of magnet is still unknown.
There some artificial magnets available in the market. These are the bar magnets. The origins of the artificial magnets are as followings –
- Bar Magnet
- Current carrying wire
- Moving Charge
We usually use bar Magnet as a source of magnetism. Scientist Oersted first observed that the current Carrying wire produces Magnetic field around it. In recent days current Carrying wires are also used as the sources of magnetism. Apart from these, a moving charge can also produce Magnetic field around it.
Definition of Magnetic field
Magnetic field is a region around a magnet inside which it can affect other magnets. It repels the same poles and attracts the opposite poles. The strength of magnetic field at a region inside a magnetic field is known as the magnetic field intensity.
If a charge q is moving with a velocity v in uniform Magnetic field then from Lorentz equation we get the Magnetic force on the charge is F= q (V × B ) .
Magnetic field strength is defined as the maximum force on an unit positive charge moving in that field with unit velocity. Magnetic field is denoted by B. It is a vector quantity. One can determine the direction of magnetic field by using Fleming’s right hand thumb rule. Again, one can determine the magnitude of magnetic field vector by using Biot-Savart law and Ampere’s Circuital law.
Properties of Magnetic field
The properties of Magnetic field are as followings –
- Magnetic force is a conservative force. That means work done by magnetic force in forward motion is equal and opposite to that of in reverse motion of same distance.
- Magnetic force may be attractive or repulsive. Magnetic force between two same poles is repulsive and the magnetic force between two opposite poles is attractive in nature.
- Strength of magnetic field decreases as the distance from the source increases.
- Magnetic field due to a current Carrying wire is directly proportional to the current flow through the wire.
- Magnetism depends on temperature. In increasing of temperature the strength of magnetic field decreases.
- Magnetic field can convert some materials into the magnets.
- Magnetic force always acts perpendicularly to the magnetic field.
Unit of Magnetic field
The SI unit of Magnetic field is Tesla (T) and the CGS unit of Magnetic field is Gauss (G). 1 Tesla = 104 Gauss.
1 Tesla = 1 Weber/m2 and 1 Gauss = 1 Maxwell/cm2.
Dimension of Magnetic field
Dimension of Magnetic field = (Dimension of Force) ÷ ( Dimension of Charge × dimension of velocity)
So, Dimensional formula of Magnetic field is [MT-2 I-1 ].
Definition of 1 Tesla Magnetic field
If a particle of charge +1C is moving with a speed 1 m/s in uniform Magnetic field and experience a maximum force of 1 Newton then then strength of magnetic field is called one Tesla.
Here, the term “maximum” is very important. It implies that the angle between the velocity and magnetic field vector is 90 degree.
On which parameters does the magnetic field depend?
Strength of magnetic field depends on the following parameters –
- The amount of current flow through the conductor that acts as the origin of magnetic field. Greater current flow gives greater magnetic field around it.
- The distance of the target point from the source of magnetic field. As the distance increases, the magnetic field decreases.
- The medium around the source.
Uniform Magnetic field
If strength of Magnetic field remains same at every point in a magnetic field then the magnetic field is the uniform magnetic field. Magnetic field lines are straight lines in uniform magnetic field. Magnetic poles experiences equal Magnetic force at every point in uniform Magnetic field.
This is all from the article “Origin and definition of Magnetic field”. If you have any doubt or question on this topic you can ask in the Comment section.
- Properties of Magnetic field lines
- Magnetic force on a current carrying wire
- How to find the direction of Magnetic field?
- Biot-Savart Law
- Electromagnetic wave: definition, properties and use
- Properties of Electric field lines.