The unit of magnetic flux density is
Tesla
Understanding the Unit of Magnetic Flux Density
The question asks about the standard unit used to measure magnetic flux density. Magnetic flux density, often represented by the symbol $\vec{B}$, is a measure of the strength of a magnetic field. It quantifies how many magnetic field lines pass through a specific area.
Identifying the Correct Unit for Magnetic Flux Density
In the International System of Units (SI), the unit for magnetic flux density is the Tesla (T). One Tesla is defined as one Weber per square metre ($\text{Wb/m}^2$). It indicates the force exerted on a moving charge in a magnetic field.
Analyzing the Given Options
Let's look at the other options provided and see what physical quantities they represent the units for:
- Farad/metre: The Farad (F) is the unit of capacitance. Farad per metre (F/m) is the unit for permittivity, which is a property of a dielectric material that affects the electric field within it. It is related to electric fields, not magnetic flux density.
- Ampere/metre: The Ampere (A) is the unit of electric current. Ampere per metre (A/m) is the SI unit for magnetic field strength, often denoted by $\vec{H}$. While related to magnetic fields, magnetic field strength ($\vec{H}$) and magnetic flux density ($\vec{B}$) are distinct quantities related by the permeability of the medium ($\vec{B} = \mu\vec{H}$).
- Ohm/metre: The Ohm ($\Omega$) is the unit of electrical resistance. Ohm per metre ($\Omega$/m) is the unit for resistivity, which is a fundamental property of a material that measures how strongly it resists electric current. It is related to the electrical properties of a material, not magnetic flux density.
- Tesla: As discussed earlier, the Tesla (T) is the SI unit for magnetic flux density ($\vec{B}$).
Therefore, based on the definitions of these units in electromagnetism, the correct unit for magnetic flux density is Tesla.
Summary of Units
Here is a brief summary of the units for the quantities mentioned:
| Quantity | Symbol | SI Unit |
|---|---|---|
| Magnetic Flux Density | $\vec{B}$ | Tesla (T) |
| Permittivity | $\varepsilon$ | Farad/metre (F/m) |
| Magnetic Field Strength | $\vec{H}$ | Ampere/metre (A/m) |
| Resistivity | $\rho$ | Ohm$\cdot$metre ($\Omega\cdot$m) - Note: Ohm/metre is not standard resistivity unit. |
| Resistance | R | Ohm ($\Omega$) |
| Capacitance | C | Farad (F) |
| Magnetic Flux | $\Phi_B$ | Weber (Wb) |
Reviewing the table and the analysis confirms that Tesla is the unit specifically associated with magnetic flux density.
Revision Table: Key Electromagnetism Units
| Quantity | Symbol | SI Unit |
|---|---|---|
| Magnetic Flux Density ($\vec{B}$) | $\vec{B}$ | Tesla (T) |
| Magnetic Flux ($\Phi_B$) | $\Phi_B$ | Weber (Wb) |
| Magnetic Field Strength ($\vec{H}$) | $\vec{H}$ | Ampere per metre (A/m) |
| Permeability ($\mu$) | $\mu$ | Henry per metre (H/m) |
| Electric Field Strength ($\vec{E}$) | $\vec{E}$ | Volt per metre (V/m) or Newton per Coulomb (N/C) |
| Electric Flux ($\Phi_E$) | $\Phi_E$ | Newton metre squared per Coulomb ($\text{Nm}^2/\text{C}$) or Volt metre (Vm) |
| Electric Displacement Field ($\vec{D}$) | $\vec{D}$ | Coulomb per square metre ($\text{C/m}^2$) |
| Permittivity ($\varepsilon$) | $\varepsilon$ | Farad per metre (F/m) |
| Electrical Resistance (R) | R | Ohm ($\Omega$) |
| Resistivity ($\rho$) | $\rho$ | Ohm-metre ($\Omega\cdot$m) |
| Electrical Capacitance (C) | C | Farad (F) |
Additional Information on Magnetic Quantities
Magnetic flux density ($\vec{B}$) and magnetic field strength ($\vec{H}$) are both used to describe magnetic fields, but they represent different aspects. $\vec{B}$ is related to the force on a moving charge or current, while $\vec{H}$ is related to the currents creating the field. The relationship between them in a linear, isotropic material is $\vec{B} = \mu \vec{H}$, where $\mu$ is the magnetic permeability of the material. Permeability quantifies how a material responds to an applied magnetic field and allows the formation of magnetic flux density.
Magnetic flux ($\Phi_B$) is the total magnetic field passing through a given area. It is calculated as the integral of the magnetic flux density over the area: $\Phi_B = \int \vec{B} \cdot d\vec{A}$. The unit of magnetic flux is the Weber (Wb). Since $\text{Wb} = \text{Tm}^2$, the unit of magnetic flux density (T) can also be expressed as $\text{Wb/m}^2$.
Important Questions from Magnetostatics
A magnetic pressure which sets up or tends to set up flux in a magnetic circuit is called-
A coil of 600 turns and of resistance of 20 Ω is wound uniformly over a steel ring of mean circumference 30 cm and cross sectional area 9 cm2. If the relative permeability of the ring is 1600. Find the value of reluctance.
The B-H curve for ______ will be a straight line passing through the origin.
The SI unit of permeability is:
Which of the following equations accurately describes the relationship between the magnetic flux density ($B$) and the magnetic field strength ($H$) in a homogeneous isotropic material, given its absolute permeability ($\mu$)?
