Ch. 2 Electromagnetic Radiation, Magnetism, and Electrostatics
1 Hz = how many cycles per second?
1 Hz = 1 cycle per second
What are the 4 types of magnetic materials?
1. Ferromagnetic 2. Paramagnetic 3. Diamagnetic 4. Nonmagnetic
Laws of Magnetism
1. Magnetic Poles 2. Repulsion-Attraction 3. Inverse Square Law
Electrostatic laws
1. Repulsion-Attraction law 2. Coulomb's law 3. Distribution law 4. Concentration law 5. Movement law
Electromagnetic radiation characteristics
1. Velocity 2. Frequency 3. Period 4. Wavelength 5. Amplitude 6. Energy 7. Intensity
3 methods of electrification?
1. friction 2. contact 3. induction
Electromagnetic spectrum in order from longest wavelength to shortest wavelength, low energy to high energy, and low frequency to high frequency
1. radio 2. radar 3. infrared 4. visible light 5. ultra violet light 6. xray 7. gamma 8. cosmic
A wave with a frequency of 2 cycles per second has a period of what?
1/2 second - one wave is completed in 1/2 second
Planck's constant
4.15 x 10 ^ -15 eVs (electron volts per second)
How many electron charges = 1 coulomb?
6.3 x 10 ^18 electron charges = 1 coulomb
In the US electricity has what frequency?
60 Hz
How many cycles per second is 60 Hz?
60 cycles per second
What is the formula that demonstrates the relationship between energy and frequency?
E = hf - E= photon energy in electron volts (eV) - h= Planck's constant - f= frequency
Inverse square law formula?
I1/ I2 = D2^2/D1^2 -I1= old intensity -I2= new intensity -D1= old distance -D2 = new distance
When a nonmagnetized material is introduced into a magnetic field, the material is magnetized, and then is removed from the magnetic field, and the material is no longer magnetized, what is this called?
Magnetic induction - works with any ferromagnetic material
What is a temporary opposite charge?
When electrification by induction occurs and the electrons will return to their original positions when the charged object is withdrawn
What surrounds a magnet or moving electric current?
a magnetic field (flux lines); all magnets are surrounded by fields
When a charged particle is in motion, what is created?
a magnetic force field
When electromagnetic radiation acts as a particle (not a wave) it is called what?
a photon or quanta
Magnetism
ability of a lodestone or magnetic material to attract iron, nickel, or cobalt
Why is every magnet bipolar?
all have a north and a south pole, even if they are broken, each piece will have a north and south pole
Paramagnetic materials
aluminum, platinum, gadolinium (MRI contrast)
The wave is demonstrated with what formula?
c = f (lambda) -c=velocity or speed of light -f= frequency -lambda= wavelength
Diamagnetic materials
copper, beryllium, bismuth, lead, and water
What is the unit of electric charge?
coulomb
Energy and frequency are _____ proportional
directly proportional
Nonmagnetic
do not react with magnetic fields
Electromagnetic radiation consists of what 2 simultaneous waves?
electric and magnetic waves at 90 degrees to each other
Concentration law
electric charges concentrate on the sharpest curvature of a conductor -they then discharge to an area of low concentration in an attempt to equalize -electrical potential
Distribution law
electric charges reside on the external surface of a conductor (like a wire) so they can stay as far away from each other as possible (repulsion-attraction law) leaving the inside uncharged
The entire band of electromagnetic energies is called what?
electromagnetic spectrum
Spin magnetic moment
electrons spinning on its axis and also spinning in its orbit (like earth)
Ionizing radiation is described as what?
energy
Magnetic Poles Law
every magnet has a north and a south pole
If the distance from the x-ray source is doubled, the intensity decreases by a factor of what?
factor of 4
Radio waves are described by what?
frequency
What is the unit of magnetism?
gauss (G) and tesla (T) -1 tesla = 10,000 gauss
Infrared radiation
has shorter wavelengths and higher energy than radar and microwaves, can heat nearby objects like a toaster
Radar and Microwaves
have shorter wavelengths and higher energy than radio waves, used in ovens, by law enforcement, and in microwave ovens
What is the unit of measurement for frequency?
hertz (Hz) - 1 Hz = 1 cycle/1 second
Velocity
how fast the radiation moves - CONSTANT (c)
Frequency
how many cycles per second are in the wave; also called rate of rise and fall (number of peaks or valleys in each second)
Where is the magnetic south pole located?
in the north pole
Where is the magnetic north pole located?
in the south pole
Wavelength and energy are ______ proportional
inversely proportional
Friction
involves the removal of electrons from one object by rubbing it with another object (balloon)
Ferromagnetic materials
iron, cobalt, nickel
What does heat do to a ferromagnetic material?
it destroys its magnetism because it rearranges the domains to a random orientation, loosing its permanent magnetism
If frequency is doubled what happens to the wavelength?
it is halved
What is wavelength represented by?
lambda
Repulsion-Attraction Law
like poles repel and opposites attract
Repulsion - Attraction law
like repels like and opposites attract
Other names for magnetic field?
lines of force, lines of flux, force fields
Radio waves
long wavelength low energy radiation waves, used in MRI, wavelengths very very long (football field)
Each atom acts as a very small magnet called what?
magnetic dipole
A group of magnetic dipoles aligned in the same direction is called what?
magnetic domains
Do paramagnetic materials retain magnetism after the magnetic field is removed?
no - so they cannot be permanent magnets
Electromagnetic radiation has what charge and what mass?
no charge and no mass
Contact
occurs when 2 objects touch, allowing electrons to move from one object to another; goes from charged to uncharged or area of high concentration of electrons to low concentration of electrons
Electrification
occurs when electrons are added or subtracted from an object (ionization)
Movement law
only negative charges move along solid conductors -protons are stuck in the nucleus
What happens to the domains in paramagnetic materials when they are placed in a magnetic field?
only some align in the same direction
In which direction does the magnetic forcefield move compared to the charged particle?
perpendicular to the particle
Induction
process of electrical fields acting upon one another without making contact if they are in close proximity and the charge is strong enough
How are the domains oriented when a ferromagnetic material is in a nonmagnetized state?
randomly oriented
Ferromagnetic
react strongly with magnets or in a magnetic field
Visible light
selectively activates cells in the eye, red has the longest wavelength and blue and violet have the highest energy and the shortest wavelengths in the visible spectrum
Electromagnetic radiation with shorter wavelengths has what kind of energy, frequency, and penetration?
shorter wavelengths have higher energy, higher frequency, and more penetration than longer wavelengths
In what waveform do electromagnetic waves move in?
sinusoidal (sine) waves as photons or quanta
Magnetic domains
small groups of atoms that make up magnetic material by aligning in the same direction (they act like tiny magnets inside the material like iron, cobalt, and nickel); they exhibit the magnetic field
What is the unit of measurement for velocity?
speed of light 3 x 10 ^8 meters per second (m/s) or 186,000 miles per second (mi/s)
All electromagnetic radiation travels at what speed?
speed of light 3 x 10 ^8 meters/second or 186,000 miles/second
Another name for stationary charges?
static electricity
All waves have what velocity?
the SAME velocity
Energy
the amount of energy in the wave
As the energy of the wave increases what happens to the amplitude?
the amplitude increases or the height of the wave increases
Wavelength
the distance between corresponding parts of the wave (from peak to peak or valley to valley)
Electric field
the electrical force exerted on a charge; around all electrical charges toward negative and away from positive charges; a charge object has a force field surrounding it, that is the electric field
Coulomb's law
the electrostatic force between 2 charges is inversely proportional to the square of the distance between them (Inverse square law)
Intensity
the flux of the energy; energy flow per second
Inverse square law
the intensity of something is inversely proportional to the square of the distance from the source
Inverse Square Law for laws of magnetism
the magnetic force between two magnetic fields is inversely proportional to the square of the distance between them
Amplitude
the magnitude of the wave (how high the peak goes from 0 or from the line of propagation in either direction)
Electrostatics
the study of stationary or resting electric charges
Period
the time for one complete cycle
Why are nonmagnetic materials not attracted to magnets?
there are an equal number of dipoles spinning in both directions
When a ferromagnetic material is placed in a magnetic field what happens to the domains?
they are aligned
Wavelength and frequency have what kind of relationship?
they are inversely related - if wavelength goes up frequency goes down
After the magnetic field is removed from a ferromagnetic material after being introduced, what happens to the domains?
they remain aligned forming a permanent magnet
Ultraviolet light
used in labs to destroy airborne bacteria and can cause sunburn
X-rays and Gamma rays
very short wavelengths, high energy, high frequency radiation, measured in kilo electron volts (keV), used for x-ray and radiation therapy
Electromagnetic radiation may appear in what forms?
visible light, x-rays, infrared, or radio waves
What is the unit of electrical potential?
volts
What is intensity measured in?
watts/cm^2
Light is described by what?
wavelength
Paramagnetic
weakly attracted to magnetic fields
Diamagnetic
weakly repelled by a magnet
Nonmagnetic materials
wood, glass, rubber, and plastics
The earth has what kind of potential? Why?
zero or ground potential because it is neutral
