Physics (Electrostatics and Magnetism Chapter 4)
fundamental unit of charge
coulomb (C)
electric current
if electric potential (voltage) is applied to objects such as copper wire, then electrons flow along the wire through a conductor and is called a electric current or electricity
resistance?
interferes with the flow of electrons
the electric field points __________ for a negative charge?
inward
the volt is potential energy/unit charge or a?
joule/coulomb (J/C)
repulsion and attraction for magnetism
like poles repel; unlike poles attract, like lines of force repel and unlike lines of force attract
the stronger the magnetic field, the greater the # of
lines of flux or greater flux density
the force fields that are created when magnetic dipoles orient to create a magnet are called?
lines of force, or lines of flux, or magnetic field
materials that have the ability to attract iron are classified as having a strong?
magnetic field
ferromagnetic
material (iron, cobalt and nickel) that is strongly attracted by a magnet and can usually be permanently magnetized by exposure to a magnetic field. these materials have a majority of their dipoles lying in the same direction, thus setting up a natural magnet.
semiconductors
material that under some conditions behaves as a insulator and in other conditions behaves as a conductor, silicon, germanium
the stronger the magnetic field the?
more lines of flux
electric resistance is measured in ?
ohms
when a charged particle is in motion, a magnetic force field _____________ to the motion will be created
perpendicular
A = ?
unit of electric current
what is the unit of electric potential or "potential difference?"
volt
V = ?
voltage
one watt is = to
1A of current flowing through an electric potential of 1V. Power (W) = voltage (V) x current (A).
Distribution
Charges reside on the external surfaces of conductors and equally throughout nonconductors.
Electric charge of a conductor is _____ along the _____ _____ of the surface.
Concentrated, Sharpest Curvature
If an electric potential is applied to objects such as copper wire, then electrons move along the wire. This is called _____ _____ or __________.
Electric Current or Electricity
induction
Electrification by induction is the process of electrical fields acting on one another without contact. ex: rubber ballon sticking to wall and happens because of repulsion and attraction
friction
Electrification by friction occurs when one object is rubbed against another, and, due to differences in the number of electrons available on each, electrons travel from one to the other
contact
Electrification by contact occurs when two objects touch, permitting the transfer of electrons to move from one to the other.
Coulomb's Law
F=K Q₁*Q₂/d², magnitude of force between two charges F = force (newton) Q1 = charge of object 1 (coulomb) Q2 = charge of object 2 (coulomb) d = distance between objects (meters) k = proportionality constant
repulsion-attraction
Like charges repel; unlike charges attract
The Coulomb's law
The force between two charges is directly proportional to the product of the electrostatic charges and inversely proportional to the square of the distance between them
Concentration
The greatest concentration of charge will be on the surface where the curvature is greatest or sharpest, ex: cattle prod
Magnetic Moment
The proton in a hydrogen nucleus spins on its axis and creates a nuclear magnetic dipole.
ohms law
V=IR V = is the electric potential in volts (V) I = is the electric current is amperes (A) R = is the electric resistance in ohms (also do triangle, V on top and I and R across from each other and underneath V)
Electric potential
a system that possesses potential energy is a system w/ stored energy, such a system has the ability to do work when this energy is released
energy?
ability to do work and can not be created nor destroyed
potential difference?
ability to move a charge; volt
CURRENT in which electrons oscillate back and forth ?
alternating current (AC)
electric current is measured in
amperes (A)
electrification is?
an excess of electrons
insulator
any material that does not allow electron flow, glass, rubber, plastic and air and other earthlike materials
conductor
any substance through which electrons flow, most metals, copper is the best, and water due to salts and impurities it contains
opposite charges?
attract
electric charges associated with an electron and a proton and have the same magnitude but different?
charges
Electrification can be created by? "electrified"
contact, friction, electric induction
the magnitude of the electrostatic force is given by what law?
coulombs law
magnetic fields are?
dipoles
electrons that FLOW in on direction along the conductor, the ELECTRIC CURRENT is called ?
direct current (DC)
1 ampere is = to an?
electric charge of 1 C flowing through a conductor each second
the smallest unit of electric charge is?
electron and proton
the force of attraction b/w unlike charges or repulsion b/w the like charges is attributable to the electric field, it is called
electrostatic force
I = ?
equation symbol for current
R = ?
equation symbol for resistance
magnetic poles
every magnet has 2 poles, a north and south pole and will always have a north and south pole even it cut in half
flux density is determined both by?
field strength and by the are in which the lines of flux are located
inverse square law for magnetism
force b/w 2 magnetic fields is directly proportional to the product of their magnitudes and inversely proportional to the square of the distance b/w them......as an object gets further away, the influencing field decreases b/c of the increased area it affects
matter
has mass, takes up space and has energy equivalence
the electric ground (Earth)
hold and acts as a reservoir for stray electric charges; in this capacity it is called an electric ground
superconductivity
is the property of some materials to exhibit no resistance below a critical temp (niobium and titanium)...electric current exists without voltage
uniformly strong magnetic field is referred to as a ?
magnet
groups of atoms w/ this net magnetic field are know as?
magnetic dipoles or magnetic domains
diamagnetic
materials, such as beryllium, bismuth and lead, are actually weakly REPELLED by all magnetic fields, including both North and South poles. water is slightly diamagnetic.
paramagnetic
materials, such as platinum and aluminum, have low permeability and weak ATTRACTION magnetic fields. only slight majority of dipoles in the same direction. MRI are usually paramagnetic
nonmagnetic
materials, such as wood, glass, rubber and plastic and NOT affected by magnetic fields and cannot be magnetized. (electrons in this material do not have the ability to freely orient themselves to external magnetic lines of force)
atoms having a significant # of electrons w/ their magnetic moments in the same direction, especially when the outer shells are involved, will exhibit a ?
net magnetic field in a distinct direction
with electrified copper wire, excess electrons are distributed on the ___________ ____________?
outer surface
the electric field points __________ for a positive charge?
outward
ease with which a material can be magnetized?
permeability
increasing electric resistance results in a ?
reduced electric current
positive charges?
repel
5 laws of electrostatics?
repulsion-attraction, the inverse square law, distribution, concentration, movement
electric circuit?
resistance is controlled, current flows in a closed path
ability of a material to stay magnetized
retentivity
magnetism is fundamental property of ?
some forms of matter
lines of force always flow _________ to __________ w/in the magnet and never intersect?
south to north
spin magnetic movement
spinning of an individual electron
magnetic poles are induced through the?
temporary orientation of the dipoles
SI unit for magnetic flux density? British unit?
tesla (T), British unit=gauss (G)
inverse square relationship
the electrostatic force is very strong when objects are close but decrease rapidly as objects separate
ohms law meaning
the voltage across the total circuit of any portion of the circuit is equal to the current times the resistance
What is the primary function of an x-ray machine?
to convert kinetic or electric energy to electromagnetic energy
when you cut a magnet in half you get?
two smaller sized magnets with north and south poles
Electric charge distribution is _____ throughout or on the surface.
uniform
omega sign = ?
unit of resistance "ohm"
electric potential
voltage
electric power is measured in
watts (W)
SI unit for magnetic flux?
weber (Wb)
magnetic induction
when a non-magnetized iron bar is brought w/in the lines of force of a strong magnet, the dipoles will temporarily align themselves w/ the lines of the force passing through the iron bar. If the bar is removed from the field after a short while, the dipoles will return to their random orientation, thus leaving the bar unmagnetized.
electric charges have potential energy b/c
when positioned close to each other, like electric chargers have electric potential energy b/c they can do work when they fly apart
electric circuits
when the resistance is controlled and the conductor is made into a closed path, the result is an electric circuit
electric charges have potential energy b/c they have the ability to do ?
work
electrodynamics
"electricity," study of electric charges in motion
the ampere is proportional to the _______ of electrons flowing in the electric circuit?
#
dipoles
-NO smallest unit of magnetism -magnetic field that always has 2 poles, north and south
magnetism?
-difficult to detect and measure -cannot sense magnetism -any charged particle has a magnetic field associated with it (in motion) -ELECTROMAGNETIC RADIATION CARRIES BOTH AN ELECTRIC AND A MAGNETIC FIELD AS IT TRAVELS THROUGH SPACE
magnetic field lines?
-leave from the north pole and enter the south pole -lines are imaginary, but may be demonstrated with a magnet and iron fillings
magnetic force
-magnetic force is proportional to the product of the magnetic pole strengths and inversely proportional to the square of the distance between them; ex: if the distance between two bar magnets is halved, the magnetic force increases by four times
1 V =
1 joule/coulomb
laws governing magnetism
1) repulsion and attraction 2) inverse square law 3)magnetic poles
1 (C) = ?
6.3 x10^18 electron charges
C/s =?
Ampere
lines of force always flow from _________ to _______ outside the magnet and never intersect?
North to south
Movement
Only negative charges move along solid conductors.
electric power
P = IV (formula) P = power in watts I = current in amperes V= electric potential in volts
