Magnetic Field and Magnetic Field strength - Fundamentals | video in HINDI | EduPoint

In this Physics video lecture in Hindi we discussed about magnetic field and strength of magnetic field or magnetic field intensity. Magneti field can be defined as the space around a magnet ( or a conductor carrying current ), in which its magnetic effect can be experienced. The strength of the magnetic field at a point is defined as the force experienced by a north pole of unit pole strength at that point. In S.I., its unit is tesla (T)
1 tesla = 1 newton 〖ampere〗^(-1) 〖metre〗^(-1)
1 tesla = 1 weber 〖metre〗^(-2)
If a magnetic pole of pole strength m is placed at a point and that pole experiences a magnetic force F, we sday the magnetic field intensity ( or strength ) at that point is F/m. Magnetic field intensity is a vector quantity and its direction at a point is the same as the direction of the force being applied on a north pole placed at that point.
Other relevant topics :-
Magnetic pole :- The preferred region of attraction near the two ends of a magnet, where the magnetic force due to a magnet is maximum, are called the poles of that magnet.
Magnetic pole strength of a pole is the strength of that pole. It depicts how strong magnetic field that pole is creating.
In S.I., its unit is A m or ampere-meter.
A magnetic pole is said to be of unit strength, if it repels an equal and similar pole with a force of 10-7 N, when placed in vacuum (or air) at a distance of one meter from it.
A magnet has following properties:-
(i) Attractive property :- A magnet can attract magnetic substances like iron, steel, nickel etc.
(ii) Inductive property :- When a magnetic material is placed near a magnet it acquires magnertism.
(iii) Directive property :- A bar magnet, when suspended freely, aligns itself approximately along geographical north-south line.
(iv) Like poles repel each other and unlike poles attract each other.
(v) Magnetic poles exist in pairs
Coulomb's law in magnetism:-
Coulomb's law in magnetism states that the magnetic force between two magnetic poles is directly proportional to the product of the magnitude of pole strengths and inversely proportional to the square of the distance between them.
F ∝ m_1 m_2
And F ∝ 1/r^2
Hence, F ∝ (m_1 m_2)/r^2
or, F = μ_0/4π (m_1 m_2)/r^2
where, μ_0 is called absolute permeability or permeability of free space and μ_0/4π = 10-7 Wb A-1 m-1
Magnetic length of a bar magnet:- The distance between the two poles of a bar magnet is called the magnetic length of that magnet.
Magnetic length is a vector quantity and its direction is from S-pole of the magnet to its N-pole. It is denoted by 2 l ⃗.
Magnetic dipole:- An arrangement of two magnetic poles of equal and opposite strengths separated by a finite distance is called a magnetic dipole.
Magnetic dipole momen:- The product of the strength of either pole and the magnetic length of the magnet is called magnetic dipole moment.
It is a vector quantity and is represented by M ⃗. Its direction is from S-pole to N-pole.
M ⃗ = m ( 2 (l ) ⃗ )
In S.I., its unit is A〖 m〗^2 or Ampere〖 meter〗^2
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