MAGNETISM ,IMPORTANT TERMS & EQUATIONS IN ELECTRICAL ENGINEERING

Summary

This video explains fundamental concepts of magnetism in electrical engineering, covering terms like magnetic fields, lines of force, and magnetic flux. It details the behavior of magnetic lines around a bar magnet and introduces key equations, such as those for magnetic flux density, magnetomotive force, and permeability. The speaker also compares magnetic and electric circuits, discussing how terms like resistance and conductance in electric circuits relate to reluctance and permeance in magnetic circuits. By the end, viewers should have a comprehensive understanding of magnetic principles and how they apply to current-carrying conductors.

Takeaways

• 🧲 Magnetic influence is invisible but represented by lines of force around magnets, known as lines of magnetization when extended to a magnet.
• 📐 Magnetic lines of force and magnetization form closed loops called lines of induction.
• ⚡ A current-carrying conductor generates a magnetic field that forms concentric circles; the direction of current and magnetic field can be determined using Fleming’s Right-Hand Rule.
• 🔄 Magnetic flux is the amount of magnetic field, denoted by the symbol ϕ, with the unit Weber (Wb).
• 🧲 Magnetic flux density (B) represents the magnetic flux per unit area and is measured in Tesla (T) or Weber per meter squared.
• 🔋 Magnetomotive force (MMF) is the cause producing magnetic flux in a magnetic circuit, and is calculated as the product of current and the number of turns in a coil, with units of ampere-turns.
• 📏 Magnetic field intensity (H), also called magnetizing force, is the MMF per unit length of the magnetic flux path and is measured in amperes per meter.
• 🧮 Permeability (μ) is a material’s ability to conduct magnetic lines of force, with the permeability of free space (μ₀) being a constant value of 4π x 10⁻⁷ H/m.
• 📉 Reluctance (S) is the opposition to the setting up of magnetic flux in a magnetic circuit, similar to resistance in an electric circuit, with units of ampere-turns per Weber.
• 🔄 Permeance is the reciprocal of reluctance, representing how easily a magnetic flux is established in a material, analogous to conductance in an electric circuit.

Q & A

What is the magnetic field around a bar magnet?

The magnetic field around a bar magnet is the region of influence around the magnet where its magnetic force is felt. This field is represented by invisible lines called lines of force, which originate from the magnet's north pole and enter the south pole.

How are lines of force and lines of magnetization related?

Lines of force represent the influence of a magnet, and when these lines extend to include the entire magnet, they are called lines of magnetization. Both types form closed loops and are known as lines of induction.

What happens when an electric current flows through a conductor?

When an electric current flows through a conductor, it creates a magnetic field around the conductor. This magnetic field forms concentric circles that are perpendicular to the direction of the current.

What is Fleming's Right-Hand Rule, and how does it apply to magnetism?

Fleming's Right-Hand Rule states that if you grasp a current-carrying conductor with your right hand so that your thumb points in the direction of the current, your fingers will point in the direction of the magnetic flux lines. This helps determine the direction of the magnetic field around the conductor.

How is magnetic flux (Φ) defined, and what is its unit?

Magnetic flux (Φ) is defined as the amount of magnetic field produced by a magnet, quantitatively. It is measured in webers (Wb).

What is magnetic flux density (B), and how is it calculated?

Magnetic flux density (B) is the amount of magnetic flux per unit area perpendicular to the flux direction. It is calculated as B = Φ / A, where Φ is the magnetic flux and A is the area. Its unit is teslas (T).

What is magnetomotive force (MMF), and how is it represented?

Magnetomotive force (MMF) is the force that produces magnetic flux in a magnetic circuit. It is represented by the product of the number of turns (N) and the current (I) flowing through the conductor, expressed as MMF = N * I, with the unit ampere-turns (At).

What does magnetic field intensity (H) represent, and how is it calculated?

Magnetic field intensity (H) represents the magnetizing force per unit length of the magnetic flux path. It is calculated as H = MMF / L, where L is the length of the magnetic path. Its unit is ampere-turns per meter (At/m).

How is permeability (μ) defined, and what is its significance?

Permeability (μ) is a measure of how well a material can support the formation of a magnetic field within itself. It is the proportionality constant between magnetic flux density (B) and magnetic field intensity (H), given by B = μH.

What is relative permeability (μr), and how is it different from absolute permeability?

Relative permeability (μr) is the ratio of the permeability of a material to the permeability of free space (μ0). It indicates how easily a material can be magnetized relative to a vacuum, where μr = μ / μ0.