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Electricity and Magnetism
Electronics
62 cards
Cards (147)
Joule
(
J
)
Unit of work done in moving one Coulomb (C) of charge
Electric Current
Any directional movement of electric charges such as electrons
Ampere
Current of one ampere is equal to one Coulomb (1C) of charge flowing through a given point in one second (1s)
Magnetism
The property of a device or material to attract bodies of iron and other magnetic material or magnets
Sources of Steady Magnetic (Magnetostatic) Field
Permanent Magnet
Electric Field changing linearly with time
Direct Current
Dipoles and Magnetic Moments
The magnetic behavior of materials can be traced to the structure of atoms
Bohr Magneton - The strength of a magnetic moment of an electron (μB) due to electron spin
The spin of the electron produces a magnetic field with a direction dependent on the quantum number ms
Electrons orbiting around the nucleus create a magnetic field around the atom
Theories of Magnetism
Weber Theory - Weber's theory assumes that all magnetic substance are composed of tiny molecular magnets
Domain Theory - A theory based on the electron spin theory
Magnetic Field
The space surrounding a magnet where magnetic forces act
Lines of Force
Lines that are used to represent the force existing in the area surrounding a magnet
Magnetic Flux (φ)
The total number of magnetic lines of force leaving or entering the pole of a magnet
Units of Magnetic Flux (φ)
Maxwell - The cgs unit of magnetic flux
Weber - The SI unit of magnetic flux
Magnetic Flux Density (B)
The number of magnetic field lines per unit area of a section perpendicular to the direction of flux
Units of Flux Density (B)
Gauss - A cgs unit of Magnetic Flux Density
Tesla - The SI, the unit of Magnetic Flux Density
Permeability
Its ability to accept, allow or setup a magnetic field is described by a numerical value called Permeability of the material
Magnetization Curve or
B-H
Curve
The B-H Curve depicts the ability of a material to accept, allow or set-up a magnetic field as it is subjected to a magnetizing force
Magnetic Hysteresis
The delayed reaction of the magnetization of a ferromagnetic material, with the change of the magnetizing force
Hysteresis
Loop
shows the relationship between the induced magnetic flux density (B) and the magnetizing force (H)
Types of Magnets
Natural
Magnets
Artificial
Magnets
- Permanent Artificial Magnet, Temporary Artificial Magnet
Types of Magnets
Natural
Magnets
Artificial
Magnets
Permanent Artificial
Magnet
Temporary Artificial
Magnet
Classification of Magnets
Ferromagnetic
Materials
Paramagnetic
Materials
Diamagnetic
Materials
Curie Temperature
The temperature above which ferromagnetic or ferrimagnetic materials become paramagnetic
Ferromagnetic
behavior disappears above the
Curie
temperature
Electromagnets
Magnets where the magnetic field intensity is directly proportional to the current flowing through a coil with a number of turns
Magnetic
Circuits
A closed path to which a magnetic field, represented as lines of magnetic flux, is confined
Magnetomotive Force (MMF)
The magnetic force that tends to set up magnetic flux, produced due to the applied electric current in the coil of N turns
Units of Magnetomotive Force (MMF)
Ampere Turns
Gilberts
Magnetic Field Intensity (H)
The magnetomotive force per unit length at any given point in a magnetic circuit
Magnetic Field Intensity (
H
) is also given by the
Biot-Savart
Law
Units of Magnetic Field Intensity
Ampere-Turns
per
Meter
Oersted
Summary of
Magnetic Units
Faraday's
Law
The magnitude of the emf induced in a circuit is proportional to the rate of change of the magnetic flux that cuts across it
Faraday's First Law
Electromotive Force (EMF) is induced whenever a conductor cuts magnetic flux
Faraday's Second Law
The magnitude of the induced emf is proportional to the relative rate of change of flux
Maxwell's Equations
Gauss
Law for electrostatics
Gauss
Law for magnetism
Faraday's
Law
Ampere's
Law (with Maxwell's Correction)
Magnetic flux
The total number of magnetic lines of force of a magnetic field
Resistors
Components limiting
electric current
or providing
voltage drop.
Fixed Resistors
Types include
Carbon Composition
and
Metal Film.
Variable
Resistors
Include
Potentiometers
and
Rheostats.
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