electricity & magnetism

x-ray equipment

primary function is to convert electrical energy into electromagnetic energy

electrostatics

study of stationary electric charges

- chemical (battery)

- mechanical (motor)

- thermal (toaster)

electrical energy can be converted to 3 forms

matter

has mass & energy, may also have electric charge

positive & negative

electric charge units

electrons & protons

smallest units of electric charge

electrons

free to move from the outermost shell of an atom to the next

protons

fixed & cannot move

negative charges (electrons)

included in most conversations of electrical charge

electrification

due to movement of electric charges

electrified

when an object has has too few or too many electrons

electrification

created by

- friction

- contact

- induction

electrostatic law

Opposite charges attract & like charges repel

electric field

each electric charge is associated to an

positive

outward electric charge

negative

inward electric charge

uncharged particles

particles that do not have an electric field

electrostatic force

force of attraction between unlike charges or the repulsion between like charges (related by inverse square relationship)

Coulomb's law

the electrostatic force is directly proportional to the product of the electrostatic charges & inversely proportional to the square of distance between them

1 C (Coulomb)

6.3 x 10^18 electron charges

potential energy

type of energy that electrical charges have

volt (V)

unit of electric potential

volt (V)

potential energy/unit charge (J/C)

conductor

any substance through which electrons flow easily

insulator

any material that does not allow electron flow

semiconductor

material that under some conditions behaves like an insulator & in other conditions behaves as a conductor

superconductor

materials that exhibit no resistance below a critical temperature

superconductor

niobium, titanium

conductor

copper, aluminum

semiconductor

silicon, germanium

insulator

rubber, glass

superconductor characteristics

- no resistance to electron flow

- no electric potential required

- must be very cold

conductor characteristics

- variable resistance

- obeys Ohm's law

- requires a voltage

semiconductor

- can be conductive

- can be resistive

- basis for computer technology

insulator

- does not permit electron flow

- extremely high resistance

- necessary with high voltage

electric circuits

measured in amperes (A)

ohm's law

the voltage across the total circuit or any portion of the circuit is equal to the current times the resistance

electric power

measured in watts (W)

1 W

current of 1 A (ampere) flowing through an electrical potential of 1 V

magnetism

any charged particle in motion creates a magnetic field

perpendicular

the magnetic field of a charged particle (such as an electron) in motion is ___________ to the motion of the particle

charged particle

in a closed loop motion in a magnetic field

magnetic field lines

perpendicular to the plane of the motion

electron spin

created when electrons behave as if they rotate on an axis

electron spin

creates a magnetic field & is neutralized in electron pairs

odd number of electrons in outer shells

creates a magnetic field in the object

magnetic fields

do not start or end like electric fields

bipolar or dipolar magnetic fields

there is always a north & south pole

magnetic dipole

small magnetic field is created by the electron orbit

magnetic domain

accumulation of many atomic magnets with dipoles aligned

magnetic moment

spinning of electric charges induce a magnetic field

magnetic moment

proton in a hydrogen nucleus spins on its axis & creates a nuclear magnetic dipole

magnetic moment

basis of MRI

- natural magnet (earth)

- permanent magnet (made of iron, compass)

- electromagnet (wire around an iron core)

3 types of magnets

magnetic susceptibility

degree to which material can be magnetized

nonmagnetic

unaffected by magnetic field

diamagnetic

weakly repelled by either magnetic pole

ferromagnetic

strongly attracted by a magnet

paramagnetic

between ferro & non; very slightly attracted & loosely influenced by magnetic field

- nonmagnetic

- diamagnetic

- ferromagnetic

- paramagnetic

4 magnetic states of matter

wood, glass

nonmagnetic state examples

water

diamagnetic state example

gadolinium

paramagnetic state example

iron, nickle, cobalt

ferromagnetic state examples

- 2

- 1 north & 1 south pole

number of poles in every magnet

proportional

the force between the poles is ____________ to the product of the magnetic pole strengths divided by the square of the distance between them

Tesla (T)

SI unit for magnetic field strength

1 T (Telsa)

10,000 gauss (G)

oersted's experiment

discovered the link between electric & magnetic forces

moving electrons

create a magnetic field

electrons moving through a wire

will produce a magnetic field with imaginary concentric line centered on the wire

right-hand magnetic field rule

ferromagnetic field (iron)

magnetic field can be intensified by wrapping a wire around

magnetic field

can be adjusted or switched on & off by changing the current flowing through the wire

electromagnetic induction

electric current is induced in a circuit if some part of that circuit is in a changing magnetic field

electric current

induced by varying magnetic field intensity

electric motor

electric current produces mechanical motion

electric generator

mechanical motion produces electrical current

transformer

alternating electrical current & electric potential are transformed in intensity