ELECTRICITY STATE OF MATTER TEST

Electrostatics

The branch of physics that deals with stationary or resting electric charges.

Electrodynamics

the branch of physics that deals with moving charges. (to be discussed after electrostatics)

Why only electrons for electricity?

Protons are tightly bound to the nucleus

Remember electron binding energy?

Difficult to remove

Electrons can move much more easily

Electrification

Describes the process of electron charges being added to or subtracted from an object

Difference between ionization?

Ionization - atom

Electrification - object

Laws of electrostatics!!!! Quiz question !!!

Repulsion-Attraction

Inverse square law

Distribution

Concentration

Movement

Remember
Ideas
During
Concentrated
Moments

Laws of Electrostatics
1^st law –

repulsion-attraction

opposites attract

Laws of Electrostatics 2nd law

Inverse square law

Force between two charges directly proportional to product of their magnitudes and inversely proportional to square of distance between them

If an object has a charge of 4 coulombs at 4mm, what will the charge be at 8mm?

4 coulombs  = (8mm)²

        x                (4mm)²

    4 coulombs   =    64

          x                   16

    64x = 64

    x = 1 coulomb

Laws of Electrostatics
3^rd law

Distribution

Charges reside on external surface of conductors

Equally throughout insulators

Attempt to repel from each other

Laws of Electrostatics
4^th law

Concentration

Greatest concentration of charges will gather at sharpest area of curvature

Why is the law of concentration of electricity important in the manufacturing process of an x-ray tube?

Sharp or rough edges could concentrate the electrons and promote discharges

Inside of tube is highly polished and rounded

Laws of Electrostatics
5^th law

Movement

Only negative charges move along solid conductors

The electrons move along a solid conductor

Methods of Electrification

—quizzzzz

Friction

Contact

Induction

Method of Electrification- FRICTION

Occurs when one object is rubbed on another

E.g., rubbing balloon on wool sweater, combing hair during winter

Electrons travel from one object to another

Ideal during cold weather/low humidity

Method of Electrification - Contact

Occurs when two objects touch

Permits electrons to move from one object to another

E.g., walking across floor (electrification by friction) and touching doorknob (electrification by contact)

Method of Electrification – Contact (Static Discharge)

Static discharge – a form of contact electrification

Releases excess energy as light photons

CONTACT DOES NOT ALWAYS OCCUR BEFORE ELECTRONS NEUTRALIZE (discharge)

Occurs when:

Difference in charges = great

Distance between = small

*Tree branch artifact

*Humidifier in dark room

Method of Electrification - Induction

Used in operation of electronic devices

Process of electric fields acting on one another without contact

Considered most important because it is used in the operation of electronic devices

Electroscope

device used to demonstrate the presence of electrons

What are the five laws of electrostatics?

Repulsion-Attraction

Inverse square law

Distribution

Concentration

Movement

What are the three methods of electrification?

Friction

Contact

Induction

What is the difference between ‘static’ and ‘dynamic?

Static – such as electrostatic, relative non-motion

Dynamic – such as electrodynamic, motion

Basic Factors of Electrodynamics

Electric current

Properties of conducting materials

Electrical circuit

Electron sources

Describing Current Flow

Electric current – electrons that are moving predominantly in the same direction

Electrons move from areas of high to low concentration

Conventional current flow

Common household wiring = 2mm/sec of actual physical movement

Electricity moves at 3x108 (300,000,000) meters/sec

Almost the speed of light

Current flow – encouraging conditions

Vacuum – space from which air has been removed (few atoms to oppose electron flow)

Some gases (Ne) – promote drifting of electrons

Conductors and superconductors

Materials that easily permit electrons to flow. It has the ability to conduct electrons

Conductors

Copper

Aluminum

Superconductor

Titanium

Material’s Conductivity

Dependent on configuration of atoms:

Valence band

Conduction band

Material’s Conductivity - Length

Directly related to resistance

The longer the length, the more the resistance

Material’s Conductivity - Diameter

Inversely related to resistance

The smaller the diameter, the more the resistance

Material’s Conductivity - Temperature

Directly related to resistance

The higher the temperature, the greater the resistance

Increased atomic motion due to increased temperature prevents electrons from flowing freely

Good conductor – Sweet green tea

Short length (short distance away from me)

Large diameter (spout is large enough to fill my glass in 2 seconds flat)

Cool temperature (how else in the summer??)

Made of the right stuff – valence of +1, +2, or +3 (has to have enough sugar or it isn’t worth it)

In addition, overlapping valence band

Insulator

Material that resist the flow of electrons.

Plastic

Rubber

glass

Good insulator – doesn’t describe SGT

Long length

Small diameter

Hot temperature

Valence of -1, -2, or -3

Separation of conduction and valence bands

Conduction band is the area beyond the valence band.

Semiconductor- defintion

Conducts or resists (can depend on temperature)

+/- 4 valence

Semiconductors

Ability to conduct under certain circumstances and insulate under others

Silicon

Germanium

Carbon – compressed??? diamond

Valence electrons +/- 4

Compounds including these can also be used as semiconductors

Boron

Aluminum

Gallium

(All have a +3 valency)

Current

Flow of electrons in a circuit.
What kills

Voltage

Force that drives current through a circuit. quantity
not deadly

Deadly Current Threshold

4mA can induce ventricular fibrillation. ( irregular heart beat)

Lethal Current Level

80-100 mA can cause death.

What is a fuse?

A fuse is a thin wire enclosed in a casing that plugs into a circuit.

What happens to a fuse when a circuit is closed?

The fuse experiences the same current as any other point along the circuit.

What is the purpose of a fuse?

To disintegrate when it heats up above a certain level to protect the circuit.

What happens if the current climbs too high in a fuse?

The fuse burns up the wire, opening the circuit.

How does a fuse protect building wiring?

By opening the circuit before excess current can damage it.

How does an electromagnet in a circuit breaker prevent short circuits?

As current increases, the magnetism around the circuit increases. If the current becomes too high, the magnet pulls itself out of the circuit, opening it before damage occurs.

What is one method used by some circuit breakers to prevent short circuits?

Some circuit breakers use a small explosive charge that ignites at a lower level than a fire would start.

What happens when the explosive charge in a circuit breaker ignites?

It pushes the breaker away from the other end, opening the circuit.

What is an electrical circuit?

A pathway that permits electrons to move in a complete circle from their source.

What material is commonly used for electrical circuits?

Copper wire

What do electrical circuits allow electrons to do?

Move in a complete circle from their source, through resisting electrical devices and back to the source.

What is a series circuit?

A circuit in which all parts are connected end to end to provide a single path of current.

How does the total potential difference of a series circuit compare to parallel circuits when all other factors are the same?

Series circuits supply greater total potential difference than parallel circuits.

What happens to the total voltage in a series circuit as more resistance is added?

The total voltage increases.

What happens to total resistance in a parallel circuit as more resistors are added?

Total resistance drops.

What happens to total amperage in a parallel circuit as more resistors are added?

Total amperage increases.

What happens to total voltage in a parallel circuit when more resistors are added?

Total voltage remains the same.

What is a characteristic of parallel circuits regarding total resistance?

Parallel circuits offer less total resistance to electrical current when all other factors are the same.

What is a disadvantage of parallel circuits?

Increased amperage may cause a short circuit, which can cause a fire.

Short Circuit

Excessive current flow causing potential hazards.

Siemens (S)

A reciprocal ohm, as in 1/R. ac and dc

Total Voltage in Series

Sum of voltages across each component.
Vt = V1 + V2 + V3

Total Voltage in Parallel

Voltage remains constant across all components.
Vt = V1 = V2 = V3

Power in Series Circuit

Calculated as P=IV, where I is current.

Total Resistance in Parallel

1/Rt = 1/R1 + 1/R2 + 1/R3

Total Current in Series

It = I1 = I2 = I3

Total Current in Parallel

It = I1 + I2 + I3

Total Resistance in Series

Rt = R1 + R2 + R3

Ohm's Law

V=IR; relationship between voltage, current, resistance.

Amperage Increase in Parallel

Adding resistors increases total current.

Power Calculation

Power is the product of voltage and current.

Conductance

Reciprocal of resistance, measured in siemens.

P- V
E- I
P- R
SI

VOLTS- PLUS

(I)CURRENTAMPS-EQUALS

RESISTANCE OHMS- PLUS

SI- SERIES

E- V
P - I
I- R
PEN

VOLTS- EQUALS

I CURRENTS AMPS- PLUS


RESISTANCE- INVERSE

PARALLEL

Radiography

Art and science of imaging internal structures.

Natural Science

Study of natural phenomena and laws.

Physical Science

Study of non-living matter and energy.

Biological Science

Study of living organisms and life processes.

States of Matter

Solid, liquid, gas based on molecular attraction.

Atomic Theory

Concept explaining matter's structure and behavior.

Dalton's Theory

Elements separated by mass; foundation of periodic table.

Plum Pudding Model

JJ Thompson's model of atom with electrons in a cloud.

Rutherford's Model

Dense nucleus surrounded by negative electron cloud.

Bohr Model

Atom resembles miniature solar system with orbits.

Subatomic Particles

Protons, neutrons, and electrons make up atoms.

Proton

Positive charge particle located in the nucleus.

Neutron

Neutral particle located in the nucleus.

Electron

Negative charge particle orbiting the nucleus.

Atomic Number (Z#)

Number of protons in an atom's nucleus.

Atomic Mass Number (A)

Sum of protons and neutrons in nucleus.

Atomic Weight

Average mass of an element's isotopes.

Periodic Table

Arrangement of elements based on atomic structure.

Electron Shells

Regions where electrons are likely to be found.

Orbital Electrons

Electrons defined by their probable location.

Electron Capacity Formula

Formula 2n² determines maximum electrons per shell.

K Shell DEFINITION

Innermost shell with highest binding energy.

Atomic Shells

Electron configuration based on 2n² formula.

K Shell

First shell with a maximum of 2 electrons.

L Shell

Second shell with a maximum of 8 electrons.

M Shell

Third shell with a maximum of 18 electrons.

N Shell

Fourth shell with a maximum of 32 electrons.