Physical Science Chapter 6 and 7

Refraction of light happens when light undergoes

a change of speed between two transparent materials

What type of electic current is produced by fuel cells and solar cells?

dc

A source of light given off as a result of high temperatures is said to be

incandescent

Light is said to travel in straight-line paths, as light rays, until it interacts with matter. A line representing the original ray before it interacts with matter is called a

incident ray

A positive and a negative charge are initially 2 cm apart. What happens to the force on each as they are moved closer and closer together? The force

increases while moving

The ratio of lthe speed of light in a vacuum to the speed of light in a transparent is called the

index of refraction

An electric field describes the condition of space around

a charged particle

To be operational, a complete electric circuit must contain a source of energy, a device that does work, and

a conductor form the source to the working device and another conductor back to the source

galvanometer

a device that measures currents from their magnetic fields

The condition of farsighedness, or hyperopia, can be corrected with a

convex lens

the unit of electric charge is the

coulomb

As the temperature of an incandescent object is increased

more raidiation is emitted with a shift to higher frequencies

Magnetism is produced by

moving charges

The photoelectric effect is best explained by condsidering light to be

moving particles

Max Planck made the revolutionary discovery that the energy of vibrating molecules involved in blackbody radiation existed only in

multiples of certain fixed amounts

Temperature

- Resistance is directly proportional to temperature

Transformers

A transformer is a device that increases or decreases voltage in an ac circuit A transformer is basically an iron ring with two sets of coils ◦The primary or "input" coil The secondary or "output" coilEnergy losses in transmission are reduced by stepping up the voltage Energy lost to resistance is reduced by lowering the current, which is what occurs when a transformer increases the voltage ◦A power plant may step up the voltage from 22,000 volts to 500,000 volts for transmission A step-down transformer at a substation near a city reduces the voltage to several thousand volts for transmission around the city ◦Additional step-down transformers reduce the voltage to 120 volts for transmission to three or four houses

Explaining Fields

Action-at-a-distance model ◦Recognizes that masses are attracted gravitationally and that electric charge and magnetic poles attract and repel one another through space Field model ◦Considers a field to be a condition of space around at mass, electric charge, or magnet and the properties of fields are described by field lines Field-particle model (i.e. standard model of particle physics) ◦A complex and highly mathematical explanation (it is a quantum field theory) of attractive and repulsive forces as the rapid emission and absorptions of intermediate particles known as force carriers ◦Explains three out of the four fundamental forces (electromagnetic, weak nuclear force, and strong nuclear force)

The operation of which of the following depends on the interaction between two magnetic fields?

All of the above

In which of the following currents is there no electron movement form one end of a conducting wire to the other end?

Alternating current

Which of the following units are measures of rates?

Amp and watt

Ionization

An atom that has gained or lost electrons is called an ion ◦The process of removing or adding electrons to an atom is called ionization Neutral atoms have no net charge Ions have net charge

Images

An image is what your eyes see as light enters it ◦A virtual image is the result of your eyes' and brain's interpretation of light rays ◦No light rays actually originate at the image ◦A flat mirror produces a virtual image ◦Curved mirrors ◦Concave mirrors (center part curved inward) can form enlarged virtual images (shaving or makeup mirrors) or real images as in a reflecting telescope ◦Convex mirrors (center part bulging outward) can be used to increase the field of vision (automobile mirrors) ◦A real image is an image from which light rays do originate ◦The image on a movie screen is a real image

You are using which description of a current if you consider a current if you consider a current to be postive charges that flow from the positive to the negative terminal of a battery?

Conventional current

The law that predicts the behavior of electrostatic forces acting through space is

Coulomb's law

which variable is inversely proportional to the resistance?

Cross-sectional area of conductor

The photoelectric effect was explained, using Planck's work, by

Einstein

Which of the following is most likely to acquire an electrostatic charge?

Electrical nonconductor

Static Electricity

Electrons can be added or removed to everyday objects ◦This is a process called charging ◦Because these electrons are confined to an object and are not moving, the object is said to have an electrostatic charge ◦Commonly called "static electricity" Since all objects are made of atoms, and all atoms contain charge, everything contains charges ◦So an uncharged object has as many positives as it does negatives

Standard Model of Particle Physics

Gravitons are hypothetical particles which could possibly explain gravitational attraction (as the exchange of virtual gravitons) ◦Not considered part of the standard model Types of particles in the standard model: ◦Fermions (leptons and quarks) ◦Gauge bosons ◦Higgs boson The force carriers that mediate the electromagnetic, weak, and strong forces are known as gauge bosons ◦Explains electrical and magnetic (electromagnetic) forces as the exchange of virtual photons ◦Explains strong nuclear forces as the exchange of gluons ◦Explains weak nuclear forces as the exchange of W and Z bosons

Electromagnetic induction occurs when a coil of wire cuts across magnetic field lines. Which one of the following increases the voltage produced?

Increased strength of the magnetic field

Which of the following can only be explained by a wave model of light?

Interference

The electrical resistance of a dc electrical conductor depends on four variables

Material Length Diameter Temperature

Electrical Conductors and Insulators

Materials may be classified according to their reaction to charges and electricity ◦An electrical conductor is a material that will easily allow the transmission of electricity ◦For example: metals and plasmas ◦An insulator will not easily allow the transmission of electricity ◦For example: rubber and glass ◦A semiconductor is a material that sometimes conducts and sometimes insulates ◦For example: silicon and germanium

The component colors of sunlight were first studied by

Newton

The general theory of relativity explains

Newton's laws of motion

Is it possible to see light without the light interacting with matter?

No

charging processes

Objects may be charged in one of three ways: ◦Friction - which transfers electrons from one object to another ◦The amber effect is an example ◦Once charged by friction, objects return to neutral state (occurs more quickly in the presence of water vapor) ◦ ◦Conduction (contact) - which charges by transferring electrons by contact with charged objects ◦ ◦Induction - which charges by redistributing charges on an object

luminous

Objects that produce their own light ◦For example: the Sun, a lightbulb, a flame ◦The Moon and other planets are not luminous; they simply reflect light

the concept that vibrating molecules emit light in discrete amounts of energy, called quanta, was proposed by

Planck

Length

Resistance is directly proportional to length

Diameter

Resistance is inversely proportional to cross-sectional area

Household Circuits

Safety devices are included to protect people and property from electrical damage ◦Fuses or circuit breakers disconnect circuits before they become overloaded and thus overheated ◦People are protected from electrical shock by: ◦Three-pronged plugs ◦Polarized plugs ◦Ground-fault interrupters A household circuit requires two wires to each electrical device: ◦An energized "load-carrying" wire which carries electrical energy from the utility ◦A grounded of "neutral" wire that maintains a potential difference between the two wires ◦If the load-carrying wire becomes damaged, contact with the housing would make you part of the circuit as a current flows through your body

In which type of circuit would you except a reduction of the available voltage as more and more resistances are added to the circuit?

Series circuit

Which of the following is not considered to have strong magnetic properties?

Silver

The Atom

The atom is composed of particles that contain charge ◦Positively-charged protons inhabit the nucleus with neutrons ◦Negatively-charged electrons orbit the nucleus

Force Fields

The electrostatic force, as with other forces, acts over a distance ◦That is, charges can exert forces on one another without touching ◦The Sun can exert a force of gravity on the Earth (and vice versa) without having to touch it ◦Magnets can exert forces on one another without touching This can be explained with the use of a force field A force field is simply the condition of space around an object ◦An electric charge effects the space around it. That affected space is called an electric field ◦A mass can warp space and cause the gravitational force (see Ch. 7). That affected space is called a gravitational field ◦A magnet creates a magnetic field space around it We can represent fields by using field lines (lines of force)

Electrostatic Forces

The force between two charged objects is repulsive if q_1 and q_2 are the same charge and attractive if they are different The strength of the force decreases as the distance between the objects increases

Particle Charges

The fundamental charge is the basis for subatomic particles' charges ◦Charge of an electron: q_e=-1.60×10^(-19) C ◦Charge of a proton: q_p=1.60×10^(-19) C ◦Charge of a neutron: q_n=0 C Again, the negative sign on the charge of the electron is simply there to indicate the type of charge

Of the following, the electromagnetic wave with the shortest wavelength is

X rays

A current-carrying wire has a magnetic field around it because

a moving charge produces a magnetic field of its own

Today, light is considered to be

a small-scale phenomenon without a sharp distinction between particle and wave properties

Green grass absorbs

all light but green light

Light interacts with matter by which process?

all of the above

Which of the following is luminous?

all of the above

The rate at which an electric current flows through a circuit is measured in units of

amp

The strength of a magnetic field around a current-carrying wire varies directly with the

amperage of the current

The special theory of relativity is

an analysis of how space and time are changed by motion

An electromagnet uses

an electric current to produce a magnetic field

generators

an electric generator is basically an electric motor running in reverse example: A loop wire rotates in a magnetic field which produces a current in the wire

electric motor

an electromagnetic device that converts electrical energy to mechanical energy

In an electric current, the elecrons are moving

at a very slow rate

A piece of iron can be magnetized or unmagnetized. This is explained by the ideea that

atoms of iron are grouped into tiny magnetic domains that may orient themselves in a particular direction or in a random direction

An idealized material that absorbs and perfectly emits electromagnetic radiation is a

blackbody

Electromagnetic radiation is given off from matter at any temperature. This radiation is called

blackbody radiation

A transformer

changes the voltage of an alternating current

You are able to see in shaded areas, such as under a tree, because light has undergone

diffuse reflection

This separation of white into its component colors is

dispersion

A prism separates the colors of sunlight into a spectrum because

each wavelength of light has its own index of refraction

A material that has electrons that are free to move throughout the material is a (an)

electrical conductor

When a loop of wire cuts across magnetic field lines or when magnetic field lines move across a loop wire

electrons are pushed toward one end of the loop

Electromagnetic induction takes place because

electrons have their own magnetic field, which interacts with an externally applied magnetic field

When an object acquires a negative charge, it actually

gains mass

An example of an electrical insulator is

glass

Green grass reflects

green light

Earth's magnetic field

has undergone many reversals in polarity

Reverse the direction of a current in a wire, and the magnetic field around the wire will

have a reversed north pole direction

Today, light is considered to be a stream of photons with a frequency related to its energy. This relationship finds that

higher-frequency light has more energy

A lodestone is a natural magnet that attracts

iron, cobalt, nickel

direct current

is a current in which electrons move around the circuit in one direction example: ◦Chemical batteries, fuel cells, and solar cells produce a direct current ◦Direct currents are utilized in electronic devices

alternating current

is a current that changes direction at a set frequency

relay

is an electromagnetic switch device that makes possible the use of a low-voltage control current to switch a larger, higher voltage circuit on and off. example:◦: A thermostat utilizes two thin, low-voltage wires in a glass tube of mercury ◦The mercury vial turns as the changes in temperature expand or contract the coil, moving the mercury and making or breaking contact with the relay circuit When the mercury moves to close the relay circuit, a small current activates the electromagnet, which closes the contacts on the large-current circuit

electromagnetic wave

is really two waves in one

Resistance

is the ratio between the potential difference (V) between two points and the resulting current (I) Resistance=(electrical potential difference)/current

An instrument that produces a coherent beam of single-frequency, in-phase light is a

laser

Fibers optics transmits information using

light

The north pole of a suspended or floating bar magnet currently points directly toward Earth's

north magnetic pole

A current-carrying wire always has

nothing in the space around the wire

Electromagnetic induction

occurs when the loop of wire moves across magnetic filed lines or when magnetic field lines move across the loop

The electrical resistance of a conductor is measured in units of

ohm

Materials that do not allow the transmission of any light are called

opaque

In which type of circuit would you expect the sam e voltage with an increased current as more and more resistances are added to the circuit?

parallel

Today, light is considered to be packets of energy with a frequency related to its energy. These packets are called

photons

If you multiply amps by volts, the answer will be in units of

power

If you multiply volts by amps, the answer will be in units of

power

A solar cell

produces electricity directly

A luminous object

produces light of its own by any method

Of the following, the electromagnetic wave with the lowest energy is

radio wave

The color order of longer-wavelength waves in the visible region is

red, orange, yellow, green, blue, violet

Electric power companies step up the voltage of generated power for transmission across the country because higher voltage

reduces the current, which lowers the energy lost to resistance

Polaroid sunglasses work best in eliminating glare because

reflected light is polarized in a horizontal direction only

A one-way mirror works because it

reflects and transmits light at the same time

A mirage is the result of light being

refracted

A pencil is placed in a glass of water. The pencil appears to be bent. This is an example of

refraction

We see a blue sky because

scattering of light by air molecules and dust is more efficient when its wavelength is shorter

Light in one plane is transmitted and light in all other planes is absorbed. This is

selective absorption

A parallel circuit has

separate pathways for the current to flow through

A glass prism separates sunlight into a spectrum of colors because

shorter wavelengths are refracted the most

An object is hot enough to emit a dull red glow. When this object is heated even more, it will emit

shorter-wavelength, higher-frequency radiation

An electric meter measures the

strength of a magnetic field

The difference in the light emitted from a candle, an incandescent lightbulb, and the Sun is basically due to differences in

temperatures

Comparing measurements made on the ground to measurements made in a very fast airplane would find that

the length of an object is shorter, clocks run more slowly, objects have an increased mass

A permanent magnet has magnetic properties because

the magnetic domains are aligned

Electrostatic charge results from

transfer or distribution of electrons

The polarization behavior of light is best explained by considering light to be

transverse waves

The current in the secondary coil of a transformer is produced by a

varying magnetic field

The electromagnetic wave model defines an electromagnetic wave as having

velocity, a magnetic field, all electric field

Polarization of light is best explained by considering

vibrating waves in one plane

An image that is not produced by light rays coming from the image but is the result of your brain's interactions of light rays is called a

virtual image

The image you see in a mirror is

virtual image

The part of the electromagnetic spectrum that our eyes can detect is

visible

The electrical potential difference between two points in a circuit is measured in unitws of

volt

A step-up transformer steps up the

voltage

According to Ohm's law, what must be greater to maintain the same current in a conductor with more resistance?

voltage

Units of joules per second are a measure called a

watt

Any part of the electromagnetic spectrum, including the colors of visible light, can be measured in units of

wavelength, frequency, energy

Earth's magnetic field is believed to orignate

with electic currents that are somehow generated in Earth's core

A kilowatt-hour is a unit of

work

material

◦Conductors have less electrical resistance, while insulators have more electrical resistance