Physics chapter 4 Electricity, Magnetism, & Electromagnetism

When you put to pieces 2 tape together, ( sticky side of one to the unsticky side of the other) & pull them apart. When you move them close to each other again, what do you observe about the force between them?

Attraction & Repulsion

___________ current is when electrons can be made to flow in one direction along the conductor.

Direct current (DC)

Lodestones are natural magnets. True or false?

Lodestone is a natural magnet. It is naturally magnetized piece of mineral magnetic. These are naturally occurring which could attract iron. Hence, the answer is true.

_______________ is a fundamental property of some forms of matter.

Magnetism

_______________ is perhaps more difficult to understand than other characteristic properties of matter like mass, energy & electric charge.

Magnetism note: we can feel mass, visualize energy & be shocked by electricity, but we cannot sense magnetism.

Lodestones would attract iron filings. The ancient observers also knew rubbing an amber rod with fur caused it to attract small, light-weight objects such as paper. They considered the phenomena to be different. We know them as ________________ & ________________ respectively.

Magnetism & Electrostatics

______________, an oxide of iron. This rodlike stone, when suspended by a string, would rotate back & forth. When it came to rest, it pointed the way to water. It was called ______________ or leading stone.

Magnetite lodestone

Ohm's Law can be written as?

V = IR V = electric potential (volts) I = electric current (amps) R = electrical resistance (ohms) note: variations of Ohm's law can be changed by using the triangle.

Associated with each electric charge is an ___________ field.

electric

_____________ & ____________ have the same magnitude

electrons & protons

If electron flow is inhibited, the circuit resistance is _____.

high

During a thunderstorm, wind & cloud movement can remove electrons from one cloud & deposit them on another (by __________). Both such clouds become electrified, one negatively & one positively.

induction

An ________ is any material that does not allow electron flow.

insulator ex: rubber, glass, clay & any earth like materials.

The ____________ of the magnetic field is represented by imaginary lines

intensity

When positioned close to each other, _______ electric charges have electric potential energy because they can do work when they fly apart.

like note: like charges repel

The electron spin creates a magnetic field, which is neutralized in electron pairs. Therefore, atoms that have an odd # of electrons in any shell exhibit a very small ___________ ________.

magnetic field

Any charged particle in motion creates a _____________ ________.

magnetic field note: such as an electron in motion, the magnetic field is perpendicular to the motion of that particle.

The direction of electric current is important. The direction of electric current is always ____________ that of electron flow.

opposite note: Physicists are usually concerned with electron flow.

The electric field points (radiates) _____________ from a positive charge. The electric field points (radiates) ____________ to a negative charge. Uncharged particles do not have an ___________ _______.

outward inward electric field

electric charges have ______________ energy.

potential

4 Electrostatic laws: 1. ________ charges attract, ______ charges repel. 2. Electric charge distribution is __________ throughout or on the ___________. 3. Electric charge of a conductor is concentrated along the _____________ curvature of the surface. 4. ___________ law.

1. unlike, like 2. uniform, surface 3. sharpest 4. Coulomb's (electrostatic force)

One object that is always available to accept electric charges from an electrified object is the ________.

Earth (principal reservoir) note: behaves as a huge reservoir for stray electric charges = electric ground.

__________________ can be created by contact, friction, or induction.

Electrification

An object is __________________ if it has too few or too many electrons.

Electrified (Electrification) note: As you gather more electrons, your whole body gains a negative charge. The extra electrons on your body are repelled from each other and seek to escape from you.

___________________ , is the science of electric charges in motion.

Electrodynamics

Magnetism & electrostatics are both manifestations of the ____________________ ________.

Electromagnetic force

__________________ , describes how electrons are given electric potential energy (voltage) & how electrons in motion create magnetism.

Electromagnetism

_____________________, is the science/study of stationary electric charges.

Electrostatics

What is Coulomb's Law?

F = k Qa Qb/d squared (electrostatic force)

Methods of charging an object: (Friction, Conduction & Induction) Rubbing a balloon with wool, this is charging by?

Friction note: rubbing 2 different materials together causes to different charges (1 negative, one positive)

Methods of charging an object: (Friction, Conduction & Induction) Balloon sticking to a wall, this is charging by?

Induction note: induction is the process of charging a neutral body by a charged body without making any direct contact. (1 object is grounded (open system)).

The Volt is potential energy/unit charge, or ________/_________.

Joule/Coulomb note: 1V = 1 J/C

Electric charge distribution is uniform throughout or on the surface. What Electrostatic law is this?

Law #2

Electric charge of a conductor is concentrated along the sharpest curvature of the surface. What Electrostatic law is this?

Law #3

electric circuit elements: __________ inhibits flow of electrons (limit flow of electrons & reduce current). _________ provides electric potential _________ momentarily stores electric charge _________ increases or decreases voltage by fixed amount (AC only) _________ allows electrons to flow in one direction.

Resistor Battery Capacitor Transformer Diode

In a _________ circuit, all elements are connected in a line along the same conductor.

Series note: since the current has to pass through each resistor in sequence through the circuit. ex: Christmas lights wired in series have only 1 wire that connects each lamp; when one burns out, the entire string of lights goes out.

The principal semiconductor materials are _____________ & ______________.

Silicon (Si) & Germanium (Ge)

Which of the following is based on electromagnetic induction? AC current Battery DC current Radio reception Solenoid

Solenoid

____________________ is the property of some materials to exhibit no resistance below a critical temperature (Tc)

Superconductivity note: looses nothing to heat. Ohm's law does not hold true for superconductors.

A list of materials called the ____________ ________, which means, " the electricity generated by rubbing 2 objects together". Order on the list tells you the relative charge.

Triboelectric charge (series) note: materials higher on the list (Tendency to gain + charges) gives some of its electrons to materials lower on the list (Tendency to gain - charges). pick any of the 2 materials on the list, rub them together.

electric potential unit is the ________.

Volt (V) note: electric potential is sometimes called voltage note: 1 V = 1 J/C

Electrical potential is measured in? Electrical resistance is measured in? Electrical current?

Volts (V) Ohms Amperes (A)

Electric Power is measured in ________

Watts (W) P=IV or P=IIR which is P=I squared x R (resistance) in ohms.

Unlike charges ___________. Like charges __________.

attract repel (electrostatic law #1)

For a material to behave as a superconductor, however, it must be made very ________ , which requires energy

cold

A ______________ is any substance through which electrons flow easily.

conductor ex: copper wire, most metals & water because it has salts & impurities.

Electrification can be created by __________, ___________ & ______________.

contact (conduction) friction (contact by rubbing) induction

Magnetism is difficult to __________ & ____________.

detect & measure

Positive charges ___ _____ move. The transfer of electrons from one object to another causes the first to be positively electrified and the second to be negatively electrified.

do not note: When an electron moves from one atom it causes that atom to have an empty spot in the outer shell. It is now positively charged.

The primary function of the x-ray imaging system is to convert __________ energy into ____________________ energy.

electric electromagnetic (x-rays) note: A conversion takes place in the x-ray tube, where most of this electric energy is transformed into heat, some of it into x-rays.

When resistance is controlled & the conductor is made into a closed path, the result is an __________ ________.

electric circuit

If an electric potential (V) is applied to objects such as copper wire, the electrons move along the wire. This is called an ____________ __________, or electricity.

electric current

We recognize electrodynamic phenomena as _____________.

electricity (electric current) note: Electrodynamics is the study of electric charges in motion.

___________________ ______________, is a means of transferring electric potential energy from one position to another, as in a transformer.

electromagnetic induction

The smallest unit of electric charge is the ___________.

electron

Electrons behave as if they rotate on an axis clockwise or counterclockwise. This rotation creates a property called ___________ ______.

electron spin note: the electron spin creates a magnetic field, which is neutralized in electron pairs.

You touch a metal door knob after walking on carpeted floor & get shocked. (by contact). Such a shock occurs because electrons are rubbed off the carpet onto your shoes ( by friction), causing you to become electrified. An object is said to be electrified if it has too few or too many _____________.

electrons

The ampere is proportional to the number of __________ flowing in the electric circuit. 1 ampere is equal to an electric charge of 1 ____________ flowing through a conductor each second.

electrons Coulomb (C) remember: mAs = m C/s s = mC , which is electrostatic charge.

Electric current , or electricity, is the flow of ____________ through a conductor.

electrons note: electric current is measured in Amps

____________ & ____________ are the smallest units of electric charge.

electrons & protons note: electron has 1 unit of negative charge & the proton has 1 unit of positive charge. Both have the same magnitude but opposite signs.

The force of attraction between unlike charges or repulsion between like charges is attributable to the electric field. This is called an ________________ ________.

electrostatic force

Only a few elements can be lined up (dipoles lined up). These elements are known as _________________.

ferromagnetic note: Soft Iron, nickel, cobalt & rare earth. These materials have magnetic dipoles that are randomly oriented until brought under an external magnetic field.

The higher the voltage, the ___________ the potential to do work.

greater note: x-ray imaging systems usually require 220v or higher.

Electrons at _______ voltage have high potential energy & ________ capacity to do work.

high high

Electrons have one unit of ___________ charge. protons have one unit of ____________ charge.

negative positive

Regarding the movement of an electric charge from one atom to another, usually ________-______ electrons move .

outer-shell note: protons are stationary.

Increasing electric resistance results in a ___________ electric current.

reduced

Resistance decreases as the temperature of the material is __________.

reduced

At room temperature, all materials __________ the flow of electricity.

resist

Modifying a conducting wire by reducing its diameter (wire gauge) or inserting different material (circuit elements) can increase its ______________.

resistance

In 1946, William Shockley demonstrated ___________________.

semi-conduction. note: this development led to microchips & hence the explosive rise of computer technology.

A ____________________ is a material that under some conditions behaves as an insulator & in other conditions behaves as a conductor.

semiconductor ex: Silicon (Si) & Germanium (Ge) note: basis for computer chips

2 basic types of electric circuits. They are __________ circuit & ___________ circuit.

series circuit parallel circuit

Electric charge of a conductor is concentrated along the _____________ curvature of the surface.

sharpest

________ electricity is the result of an imbalance between negative and positive charges in an object.

static note: Most of the time positive and negative charges are balanced in an object, which makes that object neutral.

The outer shell electrons of some types of atoms are loosely bound and can be removed easily. Removal of these electrons electrifies the substances from which they were removed & results in __________ electricity.

static note: you run a comb through your hair, electrons are removed from the hair & deposited on the comb. It now becomes electrified with too many negative charges. which now the comb can pick up tiny pieces of paper as though the comb were a magnet.

A system that posses potential energy is a system with ________ energy.

stored note: such a system has the ability to do work when this energy is released.

The electrostatic force is very ___________ when objects are close but _____________ rapidly as objects separate.

strong decreases note: This inverse square relationship for electrostatic force is the same as that for x-ray intensity.

A superconducting circuit can be viewed as one in perpetual motion because electric current exists without ___________.

voltage note: maintain a current with no applied voltage

1 Ampere is the flow of ___ Coulomb per second

1 (1A = 1C per s) note: therefore "mAs" m C/s s = mC which is electrostatic charge.

____ watt is equal to ___ A of current flowing through an electric potential of 1 V. Power (W) = voltage (V) x current (A)

1 watt is equal to 1 ampere of current flowing through an electric potential of 1 volt. P=IV -alternatively, P=IV = IIR therefore, P=I squared x R R= resistance in ohms. note: both formulas will give you same answer.

Rules for Parallel circuit: 1. The sum of the currents through each circuit element is ________ to the total circuit current. 2. The voltage across each circuit element is the __________ & is equal to the total circuit voltage. 3. The total resistance is the __________ of the sum of the reciprocals of each individual resistance.

1. equal 2. same 3. inverse

What are the 4 electric states of matter?

1. superconductor 2. conductor 3. semiconductor 4. insulator

Rules for series circuits: 1. The _________ resistance is equal to the sum of the individual resistances. 2. The current through each circuit element is the same & is ________ to the total circuit current. 3. The sum of the voltages across each circuit element is equal to the _______ circuit voltage.

1. total 2. equal 3. total

Using or building an Electroscope can demonstrate what law? (materials needed: 2 plastic sheets, 1 paper clip to hold the sheets together. 1 pen & 1 nail).

1st law, "opposites attract & like objects repel" Note: to charge the plastic sheets, you run your fingers down them. electrons will get ripped off of you and will pile onto the plastic. This makes both sheets negatively charged and they will repel each other. when you run the plastic pen through the 2 sheets of plastic nothing happens because the plastic pen is a good insulator. electrons in the pen cant move that easily. If you put the nail between the plastic sheets, the electrons will jump to the nail because its made out of metal which is a good conductor. The electrons on the plastic sheets push on the electrons in the nail. The electrons in the nail want to get away. The nail has a positive zone at the tip and the plastic sheets are negative. (opposite charges attract).

An X-ray imaging system requires ____ to _______ KW of electric power

20 - 150 KW

1 Coulomb (C) is equal to _______________ electron charges

6.3 x 10 to the 18 power

____________ current is in most applications of electricity which require that the electrons be controlled so that they flow first in one direction & then in the opposite direction. Electrons oscillate back & forth.

Alternating current (AC)

Electric current is measured in

Amperes (amps) A

Methods of charging (electrifying) an object: (Friction, Conduction & Induction) Touching an electroscope, this is charging by?

Conduction (contact without friction) note: conduction allows the charging of a neutral body with a charged body by forming a direct contact with it.(Act of just touching the 2 objects & NOT rubbing them together like friction). let charges move between 2 objects).The charges of a charged body is transferred to the neutral body.

The fundamental unit of electric charge is the _____________

Coulomb (C) 1 C = 6.3 x 10 to the 18 power electron charges

The electrostatic force is directly proportional to the product of the electrostatic charges and inversely proportional to the distance between them. This is known as ________ ________.

Coulomb's law (#4 of Electrostatic law) note: The electrostatic force is very strong when objects are close but decreases rapidly as objects separate. The force of attraction between unlike charges or repulsion between like charges is attributable to the electric field.

The magnitude of the electrostatic force is given by ______________ law.

Coulombs (like charges repel, unlike attract) F = k Qa Qb/d squared F= electrostatic force (newton) Qa & Qb = electrostatic charges (coulomb) d = distance between the charges (meters) k = is a constant of proportionality

Using 2 straws taped to a box which hold up another straw vertically with a tooth pick in the middle so it is able to swing back and forth like an axle. If you charge a separate straw with a piece of paper (by rubbing it) and also rub the straw with the tooth pick through it. place the straw with the tooth pick through it back on the other 2 straws to hold it. use the other straw you charged and try to put it close to the other straw. you should be able to move it with repulsion because they both have like charges. you have a force of repulsion. If you decrease the distance between the straws the force of repulsion decreases ( the straw moves towards the other when you decrease but moves away when you increase the distance). This experiment shows what law of electrostatics?

Coulombs law (#4)

Electric states of matter: (material) Superconductor materials are: Conductor materials are: Semiconductor materials are: Insulator materials are:

Niobium & Titanium Copper & Aluminum Silicon & Germanium Rubber & Glass

Superconducting materials such as ______________ & ______________ allow electrons to flow without resistance.

Niobium (no resistance to electron flow) Titanium (no electric potential required, must be very cold)

Electric states of matter (characteristics): No resistance to electron flow. material? State? No electric potential required. must be very cold. material? state? Variable resistance. material? state? Obeys Ohm's law, requires voltage. material? state? Can be conductive. material? state? Can be resistive, basis for computers. material? state? Does not permit electron flow. material? state? Extremely high resistance. Necessary with high voltage. material? state?

Niobium, Superconductor Titanium, Superconductor copper, Conductor Aluminum, Conductor Silicon, Semiconductor Germanium, Semiconductor Rubber, Insulator Glass, Insulator

The manner in which electric currents behave in an electric circuit is described by a relationship known as ________ law.

Ohm's law

A ____________ circuit contains elements that are connected at their ends rather than lying in a line along a conductor.

Parallel note: is a closed circuit in which the current divides into two or more paths before recombining to complete the circuit. ex: Christmas lights wired in parallel, have 2 wires that connect each lamp when one lamp burns out, the rest remain lit.

Electric charge comes in discrete units that are _____________ or _____________

Positive or Negative