Unit of Magnetic Flux - SI Unit and CGS Unit, FAQs

What is Magnetic Flux?

Magnetic flux represents the total number of magnetic field lines passing through a given surface area. It gives a measure of how much magnetic field interacts with a surface.

It is denoted by $\boldsymbol{\Phi}$ (phi).
Magnetic Flux Formula

$
\Phi=B \cdot A=B A \cos \theta
$
Where:

• $\boldsymbol{\Phi}=$ Magnetic flux (Weber, Wb)
• $\mathbf{B}=$ Magnetic field (Tesla, T)
• $\mathbf{A}=$ Area $\left(\mathrm{m}^2\right)$
• $\boldsymbol{\theta}=$ Angle between magnetic field and normal to the surface

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Units of Magnetic Flux

The SI unit of magnetic flux is: Weber (Wb)
Equivalent Units:
$1 W b=1 T \cdot m^2$
$1 W b=1 V \cdot s$
$1 W b=1 J / A$

CGS Unit: Maxwell (Mx)

$1 W b=10^8 M x$

What is Magnetic Flux Density?

Magnetic flux density is defined as the magnetic flux passing per unit area.

$
B=\frac{\Phi}{A}
$

It also represents the force acting per unit current per unit length on a conductor placed perpendicular to a magnetic field.

Alternative Formula:

$
B=\frac{F}{I \cdot l}
$

Where:

• $\mathbf{B}=$ Magnetic flux density (Tesla)
• F=Force (Newton)
• i = Current (Ampere)
• l = Length (meter)

Units of Magnetic Flux Density

• SI Unit: Tesla (T)
• CGS Unit: Gauss (G)
  $1 \text { Tesla }=10^4 \text { Gauss }$

Magnetic Flux in Different Cases

1. Uniform Magnetic Field

If magnetic field is uniform:

$
\Phi=B A \cos \theta
$

2. Non-Uniform Magnetic Field

For varying magnetic field:

$\Phi=\int B \cdot d A$

Important Concepts of Magnetic Flux

• Flux depends on area, magnetic field, and orientation
• Flux is maximum when surface is perpendicular to field
• Flux becomes zero when surface is parallel to field
• Magnetic flux plays a key role in Faraday's Law of Electromagnetic Induction

Measurement of Magnetic Flux

Magnetic flux is measured using devices like a fluxmeter or magnetometer.
Example:
If a magnetic field of 5 mT passes through an area of $0.6 \mathrm{~m}^2$ :

$\Phi=5 \times 10^{-3} \times 0.6=0.003 \mathrm{~Wb}$

Applications of Magnetic Flux

• Electric generators
• Transformers
• Induction motors
• Magnetic sensors
• Electromagnetic induction devices

Conclusion

Magnetic flux and magnetic flux density are essential concepts in physics that help explain how magnetic fields interact with surfaces and conductors. Understanding these concepts is crucial for mastering electromagnetic induction, electric machines, and modern technological applications.

Also read -

• NCERT Solutions for Class 11 Physics
• NCERT Solutions for Class 12 Physics
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NCERT Physics Notes:

• NCERT Notes Class 11th Physics
• NCERT Notes Class 12th Physics
• NCERT Notes For All Subjects