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What is Magnetic Flux? Definition, Formula, and Applications

Magnetic flux is an essential concept in physics that helps in understanding the magnetic field and its effects. Magnetic flux is used to understand many physical phenomena. This article explores what magnetic flux is, the method for calculating it, its units, and its applications.

What is Magnetic Flux

what is magnetic flux

The total number of magnetic lines emerging from a magnetic field surface is referred to as magnetic flux. It is the product of the strength of the magnetic field and the area of the surface.

You may have read the magnetic flux definition, but didn’t understand it, so let’s define magnetic flux with an example. Imagine a magnetic field in the mind in which many magnetic lines are coming out. Now, if we place a surface in the middle of it, then how many of those lines pass through this surface? That is what we call magnetic flux.

Magnetic Flux Formula

Formula of Magnetic Flux: Magnetic flux is represented by the Greek letter Φb.

                              ΦB =B⋅A⋅cos(θ)

  • Φ  is the magnetic flux. Greek letter phi is the magnetic flux symbol =  Φ,
  • B is the magntic flux density. It is the strength of the magnetic field, i.e., the density of magnetic lines in a given area. If the magnetic lines are more dense in an area, then its magnetic field strength will be higher.
  • A is the area. Magnetic lines pass through this surface, the area of the surface where the magnetic field lines are most strongly affected.
  • θ is the angle between the magnetic field lines and the normal to that surface. The normal is the line that is perpendicular to the surface, i.e., a line that is vertical to the surface.
  • When 𝜃 =0∘, the magnetic field lines are parallel to the surface, and at this position, the magnetic flux passing through it is maximum.
  • When 𝜃 is at 90∘, the magnetic field lines are perpendicular to the surface, and in this case, the value of flux is zero. Means the magnetic lines are not crossing the surface at all.

Unit of Magnetic Flux

  • The SI unit of magnetic flux is the Weber (Wb). Weber measures the total magnetic field passing through a given surface area.
  • The magnetic flux unit 1 Weber (Wb) is equivalent to 1 Tesla-meter² (T·m²).
  • In the CGS (centimeter-gram-second) system, the unit of magnetic flux is the Maxwell. 1 Weber = 10⁸ Maxwell.

Magnetic Flux Diagram

magnetic flux diagram

A magnetic flux diagram explains the magnetic field and its effect with the help of a visual representation, especially when it passes through a surface. This diagram shows how the interaction between magnetic field lines and area takes place; this clarifies the concept of magnetic flux very well.

Magnetic field lines (B) are in one direction, and a surface area is kept between those lines. If the magnetic field lines are perpendicular to the surface, then the flux is high. If the magnetic field lines are parallel to the surface, then the flux is zero, because the flux line of the magnetic field is not in the direction of the surface.

A magnetic flux diagram helps you to understand how a magnetic field passes through a surface and at what angle, due to which the amount of flux changes.

What is Magnetic Flux Density

Magnetic flux density is the number of magnetic flux lines passing through a surface per unit area. It can also be understood as the “concentration” or “density” of the magnetic field.

  • Magnetic flux density is a measure of the intensity of the magnetic field and the properties of the magnetic medium.
  • When magnetic flux is divided by surface area, it gives magnetic flux density.
  • It is denoted by (B).

Magnetic Flux Density Formula

The formula for magnetic flux density

                                                              B= Φ / A

Where:

  • B = Magnetic flux density (in Tesla)
  • Φ = Magnetic flux in Weber (Wb)
  • A = Area in square meters (m²)

Unit of Magnetic Flux Density

The SI unit of magnetic flux density is Tesla (T). The unit of magnetic flux density is named Tesla after Nikola Tesla. Tesla is defined as the magnetic flux density that will induce a force of 1 newton on a conductor carrying a current of 1 ampere, placed at right angles (90 degrees) to the magnetic field and with a length of 1 meter.

1 Tesla (T) = 1 Newton per Ampere meter(N/A⋅m)

= 1Tesla

= Kg/A . m

Magnetic flux density is the force exerted on a charged particle moving in a magnetic field.

F =  q ⋅ v ⋅ B ⋅ sin(θ)

Where:

  • F is  the magnetic force in Newtons ( N)
  • q is charge in coulombs ( C )
  • v is the Velocity of the charge in meters per second ( m/s )
  • θ is the angle between the velocity and magnetic field direction
  • B is the Magnetic flux density in Tesla ( T )

So when θ = 90∘ then B = F / qv

Dimension Formula of Magnetic Flux Density

Magnetic flux density ( B ) = F / q . v

                                               = ( M LT-2 )/( A .T ) X ( L . T-1)

                                              = M / ( A . T-2 )

                                          = MA-1T-2L-1

Where:

  • M is the mass in kg
  • A is the ampere.
  • T is time in seconds.

Magnetic Flux Dimensional Formula

Magnetic flux formula: Φ = B ⋅ A ⋅ cos(θ), which you read a while ago.

                                              = ( kg / A . s2 ) x m2

                                              = ( M / A . T2 ) X L2

                                             = ML2A-1T-1

Where:

  • M is the mass in kg.
  • A is the ampere.
  • T is time in seconds.
  • L is length in meters.

Magnetic Flux Intensity

Magnetic flux intensity is also called magnetic flux density and is represented by the symbol B. It is a vector quantity that defines both the strength and direction of the magnetic field. Magnetic flux density means how much magnetic flux is passing through a unit area.

Magnetic flux intensity B = Φ / A

Where:

  • Φ is magnetic flux.
  • A is surface area.
  • B is flux intensity.

Difference Between Electric Flux and Magnetic Flux

Electric Flux
  • Electric field lines are the total amount of electric field passing through a surface.
  • Electric flux = E . A . Cos (θ)
  • SI unit Newton meter squared per coulomb ( N-m2 / C ) or volt meter ( v-m ).
  • ΦE = ∮ E⋅dA = Qenc / ϵ0
  • Time independent
  • measures the interaction between electric field and surface.
  • Directly related to electric charge and field.
  • Field lines originate from positive charges and terminate at negative charges.
Magnetic Flux
  • Magnetic field lines are the total amount of magnetic field passing through a surface.
  • Magnetic flux = B . A . Cos (θ)
  • SI unit Weber (wb)
  • ΦB = ∮ B⋅dA = 0
  • Time Dependent
  • Measures the interaction between magnetic field and surface.
  • Related to changes in magnetic field like Faraday’s law of induction.
  • These field lines form a closed loop inside the magnet from the north pole to the south pole.

FAQ:

Defined: What is Magnetic Flux Density

Magnetic flux density is a physical quantity that indicates the intensity and direction of the magnetic field at a particular location. It is commonly used to measure the strength of a magnetic field.

Symbol of Magnetic Flux

The symbol for Magnetic Flux is ΦB​ or sometimes just Φ.

Magnetic Flux is Denoted By

Magnetic flux is denoted by the symbol Φ. It is expressed in units of Weber (Wb).

Magnetic Flux Meaning

Magnetic flux is a measure of the number of magnetic field lines that intersect a specific surface.

Magnetic Flux SI Unit

Weber (Wb) is the SI unit of magnetic flux.