Magnetic Effect of Current

Magnetic Effect of Current

Magnetic Field

The space around a current carrying conductor in which its magnetic effect can be experienced is called magnetic field.

Biot-Savart’s Law

The law states that “the magnetic field at any point due to an element of a conductor carrying a current is

(i)            Directly proportional to the strength of current

(ii)           Directly proportional to the length of the element

(iii)          Directly proportional to the sinθ , where 'θ' is the angle between the element and the line joining the element  to the point

(iv)          Inversely proportional to the square of distance between the element and the point

dB ∝ idlsinθ/r²

dB=(µo)/4π x idlsinθ/r²

Unit: - Wb/m² or tesla

µo Is called permeability of free space

µo = 4π x 10000000

Right hand Grip Rule

It states that “If conductor carrying current is held in the right hand (grasped) such that the thumb points in the direction of the current , then the direction of finger tips round the wire represents the direction of the magnetic field lines.

Maxwell’s right handed screw rule

If a right handed cork screw is rotated so that its tip moves in the direction of flow of current through the conductor, then the rotation of the head of the screw gives the direction of magnetic lines of force.

Right Hand Palm Rule

The rule states that “If the direction of the circular current is represented by the direction of the closed fingers of the right hand, then the stretched thumb will give the direction of the magnetic field”.

Ampere’s circuital Law

Theorem states that “the line integral of the magnetic field (B) around any closed path in free space is equal to µo times the total current enclosed by the path.”

∫B x dl=µo(i net)

Remaining topics will be added soon 

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Short Notes on Electro Statics

Short Notes on Electro Statics

Number of electrons =(Total charge)/(Charge of one electron)

n=q/e

    

q=ne

 Coulomb’s Law

“It states that two point charges repel or attract each other with a force which is directly proportional to the product of the magnitude of the charges and inversely proportional to the square of distance between them.”

F=1/4Πεο×q1q2/r²

Linear charge density:- λ=q/L     Surface charge density:- σ=q/A Volume charge density:-   ρ=q/V

In Coulomb’s law the charges if placed in another medium,

Then,

F medium = F air / K = 1/4Πεο×1/K×q1q2/r²

Where K is called dielectric constant of medium

E=F/q       

F=qE

Electric field due to a point charge

Consider a single point charge ‘q’ , Let ‘r’ be the vector from q to a general point P where the test charge qο is placed.

By Coulomb’s law,

F=(1/4Πεο)x(qqο/r²)x r^

E=q/qο E=(1/4Πεο)x(q/r²)x r^

The electric field vector points radially outwards if q > 0 and radially inwards if q < 0.

Electric field inside a conductor is zero.

Dipole moment

→           →  P  = q(2a)

Electric field on the axial line of an electric dipole

E=[1/4Πεο]×[(2Pr )/(r²-a²)²] E=[1/4Πεο]×[(4qra )/(r²-a²)²]

When a<<r

Then ,

E=[1/4Πεο]×[2P/r³]

Electric field on equatorial line

E=[1/4Πεο]×[P/(r²+a²)^3/2]

When a<<r

Then ,

E=[1/4Πεο]×[P/r³]

Torque of the dipole in the uniform electric field,

→      →      ζ=P × E

Electric Flux

φ=∫E.ds

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