The strength of the magnetic field is known as magnetic flux density. Magnetic flux density, also referred to as magnetic induction or simply magnetic field strength, is a measure of the intensity of a magnetic field in a given region of space.

Magnetic Flux Density Definition:
Magnetic flux density is defined as the amount of magnetic flux passing through a unit area perpendicular to the direction of the magnetic field. It is denoted by the symbol B and has units of tesla (T) or gauss (G).

Explanation:
Magnetic field strength is a fundamental property of a magnetic field. It describes the force exerted on a unit magnetic pole placed in the field. However, it does not provide information about the distribution of the magnetic field in space.

Magnetic flux density, on the other hand, provides a measure of the strength and density of the magnetic field lines passing through a given area. It takes into account the number of field lines passing through a unit area and provides a quantitative measure of the field's intensity.

Magnetic Flux Density vs. Magnetic Flux:
It is important to differentiate between magnetic flux density and magnetic flux. While magnetic flux density (B) measures the strength of the magnetic field per unit area, magnetic flux (Φ) measures the total number of magnetic field lines passing through a given surface.

Mathematically, magnetic flux (Φ) is equal to the product of magnetic flux density (B) and the area (A) perpendicular to the magnetic field:
Φ = B * A

Applications of Magnetic Flux Density:
1. Electromagnetic Devices: Magnetic flux density is crucial in designing electromagnetic devices such as transformers, motors, and generators. It helps determine the magnetic field strength required for optimal performance.
2. Magnetic Materials: Magnetic flux density is used to characterize the magnetic properties of materials. It is essential in understanding the behavior of magnetic materials and their applications in various industries.
3. Magnetic Resonance Imaging (MRI): In medical imaging, magnetic flux density plays a vital role in generating the magnetic field needed for MRI machines. The strength of the magnetic field determines the resolution and quality of the images produced.
4. Magnetic Shielding: Magnetic flux density is utilized in designing magnetic shields to protect sensitive equipment from external magnetic fields. It helps determine the shielding effectiveness required to minimize unwanted magnetic interference.

In conclusion, the strength of the magnetic field is known as magnetic flux density. It provides a measure of the intensity and distribution of the magnetic field lines passing through a given area. Magnetic flux density is a fundamental concept in electrical engineering and finds applications in various fields.