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Title: ELECTRICITY, mAGNETISM AND ELECTROMAGNETISM
Description: EASY SUMMARY GUIDE
Description: EASY SUMMARY GUIDE
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ELECTRICITY, MAGNETISM, & ELECTROMAGNETISM
Electrostatics
The study of stationary electric charges
Electric Charge
•
Positive or negative
•
It has potential energy
•
Smallest Units: electron & proton
•
Fundamental Unit (SI): coulomb (C)
•
1 C: 6 x 1018 electron charges
Electrified
•
The object that has too few or too many electron
Electrification
•
The process of adding or removing electrons from an object
•
It is created by contact, friction or by induction
Electric Ground
•
The object that behaves as a reservoir for stray electric charges
Electrostatic Laws
•
Unlike charges attract
•
Like charge repel
•
Electric field radiate out from positive charge
•
Electric field radiate toward a negative charge
•
Uncharged particles do not have electric field
Electric Field
•
The lines of force exerted on charged ions in the tissues by the electrodes
•
It causes charged particles to move from one pole to another
•
Positive charge: points outward
•
Negative charge: points toward
Electrostatic Force
•
The force of attraction between unlike charges or repulsion between like charges
•
Directly proportional to the product of the charges
•
Inversely proportional to the square of the distance between them
•
Coulomb’s Law
•
The electrostatic force is directly proportional to the product of the electrostatic charges &
inversely proportional to the square of the distance between them
Formula: F = k(QaQb/d2
Electric Potential
•
SI Unit: volt (V)
•
1 V: 1 J/C or 1 potential energy/unit charge
ELECTRODYNAMICS
Electrodynamics
•
The study of electric charges in motion
Electrical Engineer
•
Work with electric current
Physicist
•
Concerned with electron flow
Four States of Matter
•
Conductor,
Insulator,
Semiconductor, Superconductor
Conductor
•
Any substance through which electrons flow easily
•
Characteristics:
o Variable resistance
o Obeys Ohm’s law
o Requires voltage
•
Examples: copper (Z=29), aluminum (Z=13)
Insulator
•
Any material that does not allow electron flow
•
Characteristics:
o Does not permit electron flow
o Extremely high resistance
o Necessary with high voltage
•
Examples: glass, rubber & clay
Semiconductor
•
A material that some conditions behaves as an insulator & as a conductor
•
Characteristics:
o Can be conductive
o Can be resistive
o Basis for computers
•
Examples: silicon (Si-14) & germanium (Ge-32)
Superconductor
•
Any material that allows electrons to flow without resistance
•
Characteristics:
o No resistance to electron flow
o No electric potential required
o Must be very cold
•
Examples: niobium (Nb-41) & titanium (Ti- 22)
William Shockley (1946)
•
He demonstrated semiconduction
Superconductivity (1911)
•
The property of some matter to exhibit no resistance below a critical temperature
Electric Circuits
•
The path of electron flow from the generating source through the various components & back
again
Electric Current/Electricity
•
The flow of electrons through a conductor
•
Direction: always opposite the electron flow
•
It is measured in Amperes (A)
•
1 A: 1 C/s or 1 electric charge/second
Electric Potential
•
It is measured in volts (V)
•
1 V: 1 J/C or 1 potential energy/unit charge
Electric Resistance
•
It is measured in ohms (Ω)
Ohm’s Law
•
The voltage across the total circuit or any portion of the circuit is equal to the current times the
resistance
•
Formulas: V = IR; R = V/I; I = V/R
Two Basic Types of Electric Circuits
•
Series & Parallel Circuits
Series Circuit
•
All circuit elements are connected in a line along the same conductor
Rules for Series Circuit
•
Rt = R1 + R2 + R3
•
It = I1 = I2 = I3
•
Vt = V 1 + V 2 + V3
Parallel Circuit
•
Elements are connected at their ends rather than lying in a line along a conductor
Rules for Parallel Circuit
•
It = I1 + I2 + I3
•
Vt = V 1 = V 2 = V3
•
1/Rt = 1/R1 + 1/R2 + 1/R3
Direct Current
•
Electrons that flow in only one direction
Alternating Current (AC)
•
Electrons that flow alternately in opposite direction
•
60-Hz current
Waveform
•
The graphic representation of a wave
•
x-axis: time
•
y-axis: amplitude of electric current
•
AC: sinusoidal
•
DC: straight line
Electric Power
•
It is measured in watts (W)
•
1 W: 1 A (current) x 1 V (voltage)
•
Formulas: P = IV = I2R
MAGNETISM
Magnetite
•
Oxide of iron (Fe3O4)
•
Lodestone or leading stone
Magnetism
•
The fundamental property of some forms of matter
•
It has no smallest unit
Electron Spin
•
A property created when electrons behave as if they rotate on its axis
•
It is neutralized in electron pairs
•
It creates a magnetic field
Magnetic Moment
•
A nuclear magnetic dipole created when magnetic field is created by spinning electric charge
•
The basis of MRI
Dipolar/Bipolar
•
A magnet that has two poles
•
Poles: north & south pole
Magnetic Dipole
•
The small magnet created by the electron orbit
Magnetic Domain
•
An accumulation of many atomic magnets with their dipoles aligned
Magnetic Permeability
•
The ability of a material to attract the lines of magnetic field intensity
Three Principal Types of Magnets
•
Naturally occurring magnets
•
Artificially produced permanent magnets:
•
Electromagnets
Natural Magnet
•
A magnet that gets its magnetism from the Earth
Permanent Magnet
•
A magnet whose magnetism is induced artificially
•
A bar or horseshoe-shaped magnet
•
Example: compass
Electromagnet
A coil or wire wrapped around an iron core that intensifies the magnetic field
Four Magnetic States of Matter
•
Nonmagnetic, Diamagnetic, Paramagnetic, & Ferromagnetic
Nonmagnetic
•
Unaffected by magnetic field
•
Example: wood & glass
Diamagnetic
•
Weakly repelled from both poles of a magnetic field
•
Example: copper, water & plastic
Paramagnetic
•
Weakly attracted to both poles of a magnetic field
•
Example: Gadolinium (Gd-64): contrast agent in MRI
Ferromagnetic
•
It can be strongly magnetized
•
Example: alnico (Al-12, Ni-28, Co-27) & iron (Fe-26)
Magnetic Susceptibility
•
The degree to which a material can be magnetized
Wood
•
Low magnetic susceptibility
Iron
•
High magnetic susceptibility
Hysteresis
•
A condition wherein some materials that are very susceptible are also reluctant to lose their
magnetism
Pole
•
The magnetically charged end of a material
•
North & south poles
Magnetic Laws
•
Like magnetic poles repel
•
Unlike magnetic poles attract
•
Imaginary lines of magnetic field leave the north pole
•
Imaginary lines of magnetic field enter the south pole
Magnetic Induction
•
The process of making ferromagnetic material magnetic
Magnetic Lines of Induction
•
The imaginary magnetic field lines
Magnetic Force
•
The force of attraction between unlike poles or repulsion between like poles
•
Directly proportional to the product of the magnetic pole strengths
•
Inversely proportional to the square of the distance between them
Magnetic Field Strength
•
SI Unit: tesla (T)
•
Older Unit: gauss (G)
•
1 T: 10,000 G
ELECTROMAGNETISM
Luigi Galvani (1700’s)
•
He observed that a dissected frog leg twitched when touched by two different metals
Alessandro Volta
•
HE Contributed on the development of battery
•
Voltaic Pile: precursor of modern battery
o copper-zinc plates like a DagwooD
•
Modern Battery: carbon rod (+) & zinc
cylindrical can (-)
Source of Electromotive Force
•
Any device that converts some form of
energy directly into electric energy
Hans Oersted (1820)
•
He demonstrated that electricity can be used to generate magnetic fields
Right Hand Rule
•
It determines the direction of the magnetic field
Solenoid
•
A coil of wire
Electromagnet
•
A current-carrying coil of wire wrapped around an iron core
•
It intensifies the induced magnetic field
•
Advantage: magnetic field can be adjusted or turned on & off
Electromagnetic Induction
•
An electric current is induced in a circuit if some part of that circuit is in a changing magnetic field
e
...
The strength of magnetic field
2
...
The angle of the conductor to the
magnetic
field
4
Title: ELECTRICITY, mAGNETISM AND ELECTROMAGNETISM
Description: EASY SUMMARY GUIDE
Description: EASY SUMMARY GUIDE