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Magnetic Effect Of Current

Magnetic Effect Of Current revision Notes



 

Lorentz force


A charge q moving in a region where there is an electric field Lorentz forceas well as a magnetic field Lorentz force experiences a force, given by
Lorentz forceN



Biot-Savart Law


Magnetic field induction due to a current element
Biot-Savart Law
Unit: T (tesla)
(a) Magnetic induction at the center of a circular coil of radius R carrying a current I is
circular coil of radius R carrying a current I, where N is the number of turns in the coil

(b) Magnetic induction at the centre due to circular arc conductor carrying current I
centre due to circular arc conductor carrying current I
centre due to circular arc conductor carrying current I

(c) Magnetic induction about a long straight conductor at a distance r from its center
long straight conductor at a distance r from its center


(d) Magnetic induction at a distance r due to a finite length of conductor
distance r due to a finite length of conductor
distance r due to a finite length of conductor

(e) Magnetic induction along the axis of a circular coil carrying current I
along the axis of a circular coil carrying current I
where N is the number of turns, R is the radius and x is the distance of point from the center of the coil.


Force On A Current Carrying Conductor In A Magnetic Field


The force F on a straight conductor carrying a current placed in a magnetic field of induction, B is
Current Carrying Conductor In A Magnetic Field
where θ is the angle between dI and B
(a) A straight conductor of length L1 placed at right angle to B experiences a force,
right angle to B experiences a forcenewtons

(b) The magnetic field is due to a parallel conductor L2 carrying a current I2 placed at a distance r from the first conductor,
carrying a current I 2 placed at a distance r from the first conductor
The force on
carrying a current I 2 placed at a distance r from the first conductor
The force is attractive if the currents are in the same direction, and repulsive if they are in opposite directions
 


Ampere's Law


Ampere's Law


Magnetic Dipole

(a) Bar magnet
The mutual interaction force between two small magnets of magnetic moment M1 and M2 is
Bar magnet
(b) Current loop
A current loop of area of cross-section A, and number of turns N, carrying a current I is equivalent to a magnetic dipole of magnetic moment μm where
(i) μm = NIA
(ii) magnetic potential energymagnetic potential energy
(iii) mangnetic force,mangnetic force


Motion Of A Change Particle In Magnetic Field


If a charged particle is projected with velocity v at an angle θ with the magnetic field B, then it follows a helical path of radius r, its time period is T and the pitch of the helix is p
(a) Motion Of A Change Particle In Magnetic Field
(b) Motion Of A Change Particle In Magnetic Field
(c) Motion Of A Change Particle In Magnetic Field, p is the pitch of helix.
Motion Of A Change Particle In Magnetic Field


Moving Coil Galvanometer


Moving Coil Galvanometer
where c is the torisional couple per unit twist, N is the number of turns in the coil and A is the area of cross-section of the coil, and θ is the deflection in radians.


Magnetic Properties Of Substances


(a) Magnetization vector
Magnetization vector

(b) Magnetic field intensity
Magnetic field intensity, Magnetic field intensitywhere Magnetic field intensity is called magnetic susceptibility
Magnetic field intensityMagnetic field intensity, called relative permeability
Magnetic field intensity where μm is permeability of the medium
Thus, Magnetic field intensity

(c) Curie’s Law
As the temperature increases the susceptibility of paramagnetic substances decreases
Curie's Lawor Curie's Lawwhere C is  Curie’s constant
Ferromagnetic materials when heated become paramagnetic beyond Curie temperature. Thus for ferromagnetic substances
Curie's Lawwhere TC is Curie temperature

(d) Comparison among paramagnetic, Diamagnetic and Ferromagnetic materials
Diamagnetic and Ferromagnetic materials

(e) Hysteresis
When applied magnetising field is removed the magnetism B or I that remains in the material is called retentivity. In figure, OX = OU = retentivity.
  The magnetizing force or H applied in negative –direction to make retentivity zero is called coercivity. In figure OY   = OV = coercivity
Hysteresis


Terrestrial Magnetism


Vertical component of earth’s magnetic field Terrestrial Magnetism
Horizontal component of earth’s magnetic field,Terrestrial Magnetism
where Terrestrial Magnetism = Resultant magnetic field
θ = angle of dip

φ = angle of declination
At magnetic equator, θ = 900
At magnetic pole, θ = 900
Terrestrial Magnetism
Terrestrial Magnetism

 


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