RT 205 Electromagnetic Flashcards
Electrostatics
The branch of physics that deals with the force exerted by a static
Electric Field
An effect produced by an electric charge that exerts a force on charged objects in its vicinity
Fundamental Force
Material with the ability to attract iron
Orbital magnetic moment
Magnetic field perpendicular to the motion of a charged particle
Spin magnetic moment (Electron spin)
Magnetic effect established by electrons spinning on their axis
Magnetic Resonance Imaging
Disruption of the axial spinning and energy released as domains reorient themselves
Magnetic dipoles (aka Magnetic domains)
Groups of atoms with their net magnetic field moving in the same direction
(Theorized: about 10^15 atoms make up a dipole)
Magnetic Field (aka Lines of force (flux))
Force fields formed when magnetic dipoles orient to create a magnet
Lines of force always flow from ________ to _________ outside the magnet, and flow from ________ to _________ inside the magnet.
Flow from north to south outside the magnet
Flow from south to north within a magnet
SI unit: Lines of Force
Weber (Wb)
A magnet that is moved in space near a second magnet experiences a _____________.
Magnetic Field
The strength of the magnetic field is ________ when lines are closer, and ________ when they are farther apart.
Great when lines are closer, and weak when farther apart
Magnetic flux=
Field strength/area
Measure in Tesla (T) and Gauss (G)
1 Tesla= 10,000 G= 1 Wb/m^2
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The earth’s magnetic field thought to originate with moving charges = ________T or _______G
= 0.0001 or 1 G
Classifications of Magnets Iron oxide (magnetite) remains on earths magnetic fields
Natural
Classifications of Magnets
Manufactured from steel alloy
ex. Aluminum, nickel, cobalt
Artificial permanent
Classifications of Magnets
Temporary magnet produced by moving electric current (Electron current creates magnetic field)
Electromagnets
Laws of Magnetism
Repulsion- attraction
Like poles repel,Unlike poles attract
Like lines of force repel, Unlike lines of force attract
Laws of Magnetism
Inverse square law
Force between two magnetic fields directly proportional to product of their magnitudes and inversely proportional to square of distance between them.
Ease with which a material can be magnetized
Permeability
Ability of a material to stay magnetized
Retentivity
Ferromagnetic
Material with high magnetic permeability
Imposes little resistance to orientation in presence of a magnetic field
(Ex. Iron, Steel, Nickel)
Paramagnetic
Materials with a weak attraction to magnetic fields
-Low Permeability
(Ex. Platinum, Aluminum, MRI Contrast)
Diamagnetic
Weak form of magnetism exhibited only in presence of magnetic field
(Ex. Beryllium, bismuth, lead, water)
Nonmagnetic
Materials not affected by a magnetic field and cannot be magnetized
(Ex. Wood, Glass, Plastic)
A device that stores energy and makes it available in an electrical form
Battery
A device for creating or storing electrical energy composed of several similar (usually identical) cells that are connected together
Electrical battery
Electrical cell
A single such unit, possibly one cell in a battery of multiple cells or possibly the entire device
1V=__ Joule/Coulomb
1 V= 1 Joule/Coulomb
A coil consisting of a series of loops, and serves to increase the flux density
Solenoid coil
Electromagnetic relay
Similar to circuit breakers
- Protect Technologists from high voltage when flowing
Three ways to create motion between lines of force and a conductor
- Magnetic field
- Conductor
- Relative motion
Methods to Induce a Current
- Move conductor through stationary unchanging strength magnetic field
- Move magnetic lines of force across conductor with unchanging strength magnetic field
- Vary strength of stationary magnetic field through conductor
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Four Factors of Faraday’s Law
- The strength of the magnetic field
- The velocity of the magnetic field as it moves past the conductor
- The angle of the conductor to the magnetic field (lines of flux)
- The number of turns in the conductor
Lenz’s Law
An induced emf generates a current that induces a counter magnetic field that opposes the magnetic field generating the current
Mutual Induction
The production of an electromotive force (emf) or voltage in an electric circuit caused by a changing magnetic flux in a neighboring circuit.
Self-Induction
Property whereby an electromotive force is induced in a circuit by a variation of current in the circuit itself.
Opposition to the flow of AC current produced by an inductor. (Measured in Ohms and varies in direct proportion to frequency)
Inductive Reactance
