Revision: Magnetic Effects of Current and Magnetism CUET (UG) Magnetic Effects of Current and Magnetism

Current passed through each of the two infinitely long parallel straight conductors kept at a distance of one meter apart in vacuum causes each conductor to experience a force of 2 × 10^-7 newton per meter length of the conductor.

A long solenoid is a coil whose length is much greater than its radius, producing a uniform magnetic field inside and nearly zero field outside.

The current sensitivity of a galvanometer is defined as the deflection produced in the galvanometer when a unit current flows through it.  
Mathematically, it can be given by:

I_S = `(NBA)/k`

Where k is the couple per unit twist.

Current sensitivity is defined as the deflection e per unit current.

The temperature above which a ferromagnetic substance becomes paramagnetic is called curie temperature. 

A line that joins all the places on earth, having the same angle of declination is called an isogonic line.

A line which joins all the places on earth, having zero angle of declination is called agonic line.

The path in a magnetic field in which a unit north pole tends to move when allowed to do so is known as magnetic field lines of force.

A line joining all the places on globe, having same angle of dip or inclination is called isoclinic line.

\[\vec{E}=\frac{1}{4\pi\varepsilon_0}\frac{Q}{r^2}\hat{r}\]

\[\vec{B}=\frac{\mu_0IR^2}{2(x^2+R^2)^{3/2}}\hat{i}\]

Where:

• I = current
• R = radius of loop
• x = distance from centre along axis
• μ0 = permeability of free space

B = μ₀​nI

Where:

• μ_0​ = permeability of free space
• n = number of turns per unit length
• I = current

\[\vec{m}=I\vec{A}\]

For N turns:

\[\vec{m}=NI\vec{A}\]

Tangent law states that, if a magnetic field ‘B’ is applied at right angles to the horizontal component of the earth's field B_H, the needle comes to equilibrium at an angle ‘$\theta ’$ to the magnetic meridian such that, tan θ = `B/B_H`.