# Magnetic flux and Magnetic density

**Question:** Define mafnetic flux, maximum magnetic flux, minimum magnetic flux, magnetic flux through curved surface and give unit of magnetic flux and define flux density and give its unit?

**MAGNETIC FLUX**

The.dot product of uniform magnetic field Band vector area Ā of plane element is called magnetic flux. It is denoted by **ΦB**

**ΦB = B . A**

**⇒ ΦB = BA Cos ****θ**

Here A is a vector area of plane element whose direction is along the normal to the surface of the element and Ө is the angle between the directions of the vectors B and A.

**MAXIMUM MAGNETIC FLUX**

When magnetic field is directed along normal to surface area (A) and parallel to vector area (Ā), Ө is zero, and the flux is maximum.

**ФB = B.A = BA Cos O****°**

**= BA (1)**

**= BA (max.)**

**MINIMUM MGNETIC FLUX**

When magnetic field B is perpendicular to vector area (Ā). Then Ө = 90° and the flux is minimum (Zero).

**ΦB = B. A = BA Cos 90°**

**= BA (0)**

**= 0 (minimum).**

**MAGNETIC FLUX THROUGH CURYED SURFACE IN NON, UNIFORM MAGNETIC FIELD**

When curved surface is placed in a uniform magnetic field, the curved surface is divided into a number of small surface elements each element assumed plane and the flux through the whole curved surface is calculated by taking sum of all contributions of the surface.

**ΦB = BA = N / A x m ✖️ m²**

**NmA-1 = Wb (weber)**

**MAGNETIC FLUX DENSITY**

Magnetic flux per unit area of a surface perpendicular too is called magnetic flux density. It is also called magnetic induction or magnetic field strength. It is denoted by B.

**ΦB = BA**

**B = ΦB / A**

**UNIT**

**B = ΦB / A = Wb / m² = Wbm-²**

**NA-1m-1 or Tesla**

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