Physical Science Final Exam - 8

What is the difference between an electric force and an electric charge

Electric Force: a fundamental force of nature that can attract or repel objects; Electric Charge: a fundamental quantity underlying electric force and all electric phenomena

Name two kinds of electric charges

Positive-protons; negative-electrons

Like charges repel and unlike charges attract

Like charges repel and unlike charges attract

What is the usual charge of an electron

Proton? Neutron? Electrons are negative, Protons are positive, and Neutrons are neutral

What do we call atoms that lose 1 or more electrons

Positive ions

What do we call atoms that gain 1 or more electrons

Negative ions

What is an electric conductor

Materials that allow easy flow of charged particles

What is an electric insulator

Materials that have tightly bound electrons and do not allow electrons to move easily

What is meant by "conservation of charge

" Electrons can not be created or destroyed so during the charging process electrons are just transferred from one material to another

Summarize Coulomb's law

It is basically the inverse square law that Newton discovered for electricity. Bigger charges=stronger force, farther apart=weaker force

What are the main differences and similarities between gravitational and electrical forces

Gravity - only attracts; Electricity - both attracts and repels; Both - act between things not in contact with one another, act in straight-line direction between masses or charges, force field

What is electric polarization

DIstortion of charge in an atom or molecule, balloon on the wall

What is an electric field

Occupies the space that surrounds any charged object, is a vector quantity, obeys the inverse-square law

What is the direction of electric fields

Away from positive and toward negative

What is electrical potential energy

Energy possessed by a charged particle due to its location in an electric field

What is electric potential

Energy that a source provides to each unit of charge

What are the units for electric potential

Volts

What are the units for electric potential energy

Joules

What are the units for charge

Coulombs

Charges in a conductor tend to flow from high potential to low potential

Charges in a conductor tend to flow from high potential to low potential

How are water and electric circuits similar

The higher reservoir flows to the lower reservoir until there is no difference, the valve is like the switch and a small pipe is the same as resistance

What is an electric current

The flow of electric charge

How is electric current measured

Amperes

Name and explain two types of current

DC-direct current, flows in one direction; AC-alternating current, alternate in direction

What is electrical resistance

How does this affect electric current? How well a circuit component resists the passage of electric current, the more resistance, its an insulator and the less resistance, conductor

What are some factors that affect resistance

Thin wires resist more than thick wires; Long wires resist more than short wires

Summarize Ohm's law. Tell what factors are directly or inversely related

Voltage pushes current and resistance resists it, Current is directly proportional to voltage and current is inversely proportional to resistance

Name and describe the two types of electric currents

Series - single-pathway; Parallel - branched pathway

Can you ever have a single pole in a magnet

No

What is magnetic force

Force of attraction or repulsion between a pair of magnets depends on which end of the magnet is held near the other

How are magnetic forces similar to electric forces

Likes repel and opposites retract

What is a magnetic field

Magnetic fields occupy the space around the magnet

What produces a magnetic field

Moving electric charges

What are magnetic domains

Clustered regions of aligned atoms

How do magnetic domains affect the strength of a magnet

The more magnetic domains that are aligned, the stronger the magnet is

What is formed around a current-carrying wire

Magnetic Field forms a pattern of concentric circles

What happens to the magnetic field intensity if you loop the current-carrying wire

The intensity increases the more you loop it

How can you increase the strength of an electromagnet

Increasing the number of loops and increasing the current in the coil

What do charged particles do when moving through a magnetic field

They experience a deflecting force

How does Earth's magnetic field protect us from cosmic radiation

Earth's magnetic field deflects many charged particles that make up cosmic radiation

What can the magnetic force change about a moving charged particle

Direction

How does a magnet and a wire induce voltage

Change of magnetic field strength in a coil of wire

Summarize Faraday's Law

The induced voltage in a coil is proportional to the number of loops, multiplied by the rate at which the magnetic field changes within those loops

What happens to the resistance of a magnet through a coil of loops the more loops you make

More loops=more resistance

How are generators and motors similar and different

Generators - opposite of motor, converts mechanical energy into electrical energy via coil motion, produces alternating voltage and current; Motors - different from galvanometer in that each time the coil makes a half rotation, the direction of the current changes in cyclic fashion to produce continuous rotation; Both - rotating loop

Explain briefly how generators produce sufficient quantities of electricity to light cities

A stream hits a magnet, that makes a magnetic field hitting the coils, heating the filament and lighting the bulb

How do transformers step down voltage

1 voltage/number of 1 turns=2 voltage/ number of 2 turns

Why are transformers used in electric grids

A step up transformer, steps up the voltage to be transferred and then reduces it before it enters homes

How are electric and magnetic fields related

They induce one another

What can be produced by the induction of electric and magnetic fields

Light

What is the difference between a vibration and a wave

A vibration is a wiggle in time but a wave in a wiggle in space and time that transports energy.

What is a crest

The high points of the wave

What is a trough

Low points of the wave

What is amplitude

Distance from the midpoint to the crest or trough

What is wavelength

Distance from the top of one crest to the top of the next crest, or distance between successive identical parts of the wave

What is frequency

Number of to-and-fro vibrations in a given time unit: 1 vibration per second = 1 Hertz

What is period

The time it takes for a complete vibration

What is the relationship between frequency and period

They are reciprocals

What is the formula for wave speed

Speed = wavelength X frequency

What is the difference between transverse and longitudinal waves

Longitudinal is parallel, transverse is perpendicular

What is the approximate speed of sound in air at room temperature

340 m/s

What substances do sound waves travel through faster

Diamond, Beryllium, Steel, but it is solid

What happens when sound waves are reflected

It creates an echo

What happens to waves in diffuse reflection

It is reflected in many different directions

What is refraction

The bending of a wave due to a change in the medium and/or speed of the wave

What is natural frequency

Own unique frequency, dependent on elasticity and the shape of the object

What is the difference between forced vibration and resonance

Forced vibration is the setting up of vibrations in an object by a vibrating force but resonance occurs whenever successive impulses are applied to a vibrating object in rhythm with its natural frequency

Name the two types of interference and what happens to the waves when they combine

Constructive and destructive inference, when they combine they cancel out

What kinds of waves can undergo interference

Any wave

Be able to describe the doppler effect and why it occurs

It is a perceived change in sound. Making a noise and in motion

What is a bow wave

The wave pattern made by a bug swimming at wave speed

What is a shock wave

A pattern of overlapping spheres that form a cone from objects traveling faster than the speed of sound

How does music look when it is graphed

It has steady waves, it has a frequency (repeatable wave), wavelength, and speed

What is light

How is it created? Light is electromagnetic waves created by vibrating electric charges having frequencies that fall within the range of sight

What kind of wave are all EM waves

Transverse

What is an electromagnetic wave made up of

Vibrating electric and magnetic fields that regenerate each other by electromagnetic induction

List the main categories of EM waves from lowest to highest frequency

Radio waves; Microwaves; Infrared; Visible Light; Ultraviolet; X rays; Gamma rays

Why do wet surfaces usually look darker than dry surfaces

The transparent wet region absorbs some of the energy and reflects some away from your eyes

How is light transmission similar to sound transmission

Light incident on matter forces some electrons in matter to vibrate

Describe how light penetrates a pane of glass

The electrons in the atoms of the glass start vibrating because energy is absorbed. Then the vibrating electrons emits either a photon or transfers the energy into heat. Light slows down due to the time delay between absorption and remission of photons

What is the speed of light traveling in a vacuum

300,000,000 m/s

What happens to the speed of light as it enters the atmosphere

Water? Glass? The speed of light slows down

What is reflection

The returning of a wave to the medium through which it came when encountering a reflective

Explain the law of reflection

Angle of incidence = angle of reflection

What is a virtual image and how does it look in a plane mirror

An image that is the same size as the object, formed behind a mirror and located at the same position where the extended reflected rays converge, it looks like it is as far behind the mirror as the object is in front of the mirror

How does reflection change in a curved mirror

It makes it either smaller or bigger than the original image

How does diffused reflection help us to see at night in the car

Why are wet roads difficult to see in the dark? Because the light is going in all different directions including our eyes. Wet roads are hard to see when driving because they are flat so they only reflect away from you

Give examples of refraction affecting light in water

Looks like the object or light is bending, closer to the surface

Give examples of refraction affecting light with the sun

Atmospheric refraction makes it seem like the sun is in a different spot

Give examples of refraction affecting light with mirages

Atmospheric refraction makes a dry surface look wet or reflective because of refraction

What does the color we see depend on

Frequency of light

What is selective reflection

Most objects don't emit light, but reflect light. A material may absorb some of the light and reflect the rest

What is selective transmission

The color of a transparent object depends on the color of the light it transmits

How do our eyes perceive color

Through three different types of cone receptors that are each stimulated by only certain frequencies of light

What are the primary colors of light

Red, green and blue

What colors are made when the primary colors combine

Magenta; Cyan; Yellow

What is dispersion

Process of separation of light into colors arranged by frequency. Ex. Rainbows

What is polarization

Alignment of transverse electric vectors in electromagnetic waves. This is a property of transverse waves

What happens when light is polarized

When light is polarized it aligns the waves of each filter so you can't see

What was Moseley's brilliant discovery

Each element has a different code