TAKS Objective 5

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TAKS Objective 5

• Heat, Waves and the Electromagnetic Spectrum

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Energy

• Is defined as the Ability to do Work
• Energy has Two
• Types

Kinetic (Energy of Motion) and Potential (Stored
Energy)
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Law of Conservation of Energy

• Energy can change forms, but is never created
  nor destroyed
• Loss in one form gain in an another form
• A falling object speeds up as it falls to the
  ground PE decreases as KE increases. The KE it
  has at impact the PE it had before it fell.

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Potential Energy 2 possibilities

• Gravitational PE -Object lifted to some height
• Elastic PE - A stretched or compressed object
  (spring or rubber band)

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Elastic Potential Energy

• 5 According to the data in the table, about how
  far can a spring be expected to stretch when a
  force of 3.92 N is applied?
• A 10.5 cm
• B 13.6 cm
• C 14.0 cm
• D 17.3 cm

Although this question is about reading the
table, it does show that a stretched spring can
do work (force x distance). Look at the numbers,
as Force increases by 0.98, the distance doubles,
so the answer would be
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Kinetic Energy

• KE ½ m v 2
• Ex A moving car has the ability to
• do work on the light pole if it hits it.

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Weight Mass (m) X gravity (g)

• Weight Unit of mass kg
• Unit of acceleration m/s/s
• Unit of weight Newton
• 1 Newton about ¼ pound

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On Earth gravity 9.8 m/s/s

• For every second that an object falls its speed
  increases by 9.8 m/s

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Universal Law of Gravitation

• Gravity varies depending on two factors

1) the mass of the object doing the pulling, and
2) the distance from the center of that object
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Universal Law of Gravitation

• All objects in the universe attract each other by
  the force of gravity

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• 46 Which of these would cause the gravitational
  force between Earth and the sun to decrease?
• F An increase in the length of a day on Earth
• G An increase in the distance between Earth and
  the sun
• H An increase in the number of planets orbiting
  the sun
• J An increase in the masses of Earth and the sun

What are the 2 factors that effect gravity?
Distance and Mass, to decrease distance,
increase mass. . . .
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Physics is the study of energy and provides
answers to our energy needs

• To use mechanical energy to do work such as grind
  wheat or churn milk into cheese saves fossil
  fuels and electricity.
• Using solar energy to produce heat or hot water
  also saves electricity.

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Waves - Energy carried by rhythmic disturbances

• Two types
• 1. Electromagnetic radiation moves through empty
  space
• 2. Mechanical requires a medium (air, water or
  any type of matter) for movement

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Waves - 2 Types
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Try this one

• 10 Which label on the model represents a
  wavelength?
• F Q
• G R
• H S
• J T

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All waves have similar properties

• Frequency- the number of vibrations per second or
  the speed of the movement of the vibrating
  particles
• Amplitude the size of the movement of the
  vibrating particles
• Both are controlled by the disturbance that
  created the waves

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Longitudinal or Compress ional Waves

• Vibrating particles move back and forth along the
  direction of the wave velocity
• The wave consists of compressions and
  rarefactions
• Ex. Sound Waves

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Transverse Waves

• In Transverse Waves particles vibrate at right
  angles to the direction the wave travels.
• Ex. Electromagnetic Waves, water waves or
  wiggling rope.

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Sound Waves are Compression Waves

• Sound is produced when a compression is made.
• It requires a producer and a medium to travel
  through.
• The more elastic the object, the faster sound
  travels.

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Sound acts like other waves

• Echoes are reflected sound waves
• Sonar uses echoes to judge distance to
  obstructions
• Human hearing is 20-20,000 Hz. Below 10 Hz is
  infrasonic, and above 20,000 Hz is ultrasonic.
• Resonance occurs when one vibrating object sends
  compression waves that begins another object
  vibrating at the same frequency.

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Sound Waves move through matter not through empty
space.

• 32 One tuning fork is struck and placed next to
  an identical fork. The two forks do not touch.
  The second tuning fork starts to vibrate because
  of
• F interference
• G the Doppler effect
• H resonance
• J standing waves

Resonance is the vibration of another object
struck by a wave of the correct frequency. Since
the forks are identical, the second one receives
the correct frequency to begin vibrating.
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And the answer is?
J 3300 Hz

• 38 At 0C sound travels through air at a speed of
  330 m/s. If a sound wave is produced with a
  wavelength of 0.10 m, what is the waves
  frequency?
• F 0.0033 Hz
• G 33 Hz
• H 330 Hz
• J 3300 Hz

Use the formula chart!!! Velocity f ? OR 330
m/s f x 0.10 m
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Velocity of all waves - vf ?

• f-frequency and ? is wavelength (distance between
  identical points on two consecutive waves)
• Reflection- bounce off barriers in regular ways
• Refraction- waves bend when speed changes by
  entering a different substance

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Movement of Waves

• When waves hit a barrier, they bounce off at the
  same angle that they were at when they hit. (Law
  of Reflection)
• They continue through a barrier break at the same
  pattern and speed they were at previously.

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Increasing or Decreasing wave energy

• Constructive interference adds energy to the wave
  as the crest meets crest or trough meets trough.
  
• Destructive interference causes the wave to be
  slowed or stopped by crest meeting trough. It
  cancels the amplitude of the wave.

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Electromagnetic Spectrum
All of the forms of radiation given off by
vibrating electric charges

• Radiation comes in the form
• of vibrating or throbbing
• bundles of energy called
• photons
• The frequency of the vibrating
• electric charges determines
• which type and how much
• energy will be given off

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The entire E.M. Spectrum in order from lowest to
highest frequency

• Radio waves AM and FM
• Microwaves cooking
• Infrared heat
• Visible (ROYGBV)
• Ultraviolet tanning
• Xrays medical
• Gamma

deadly radioactivity
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Nuclear Reactions

• Fusion occurs when two atoms
• combine to form a new element.
• The sun and other stars produces all of their
  energy through fusion.
• Two hydrogen atoms combine
• to form a Helium atom from the
• great gravitational forces and
• pressure in the suns core

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Nuclear Reactions - Fission

• Fission is the splitting of nucleii of large
  atoms such as Uranium and Plutonium
• Produces large amounts of ionizing radiation and
  all of the EM forms including Gamma Rays
• Currently, it is the main form of Atomic Energy
  on Earth

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Radiant Energy or Electromagnetic Energy (EM)

• All radiant energy travels at 3.0 x 108 m/sec in
  space or 186,000 miles/sec
• Velocity of a wave wavelength x frequency
• Visible light is just one type of EM Energy

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Thermal Energy

• A body contains internal KE due to the motion of
  its atoms ( they are constantly wiggling and
  jiggling)
• Thermal Energy is the total internal KE of an
  object
• Temperature is the average KE of a substance

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Heat- Transfer of Thermal Energy
Three forms of heating

• 1. Conduction-direct contact, a pot heating on a
  stove (solids)
• 2. Convection- heating by circulating fluids,
  (gas and liquid) heating from a fireplace
• And. . .

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3. Radiation Transfer of Electromagnetic (E.M.)
Energy

• Objects are heated when exposed to infrared
  radiation
• The suns heats the earth by sending infrared
  radiation along with other forms of E.M. energy
  3.0 x 108 meters through empty space

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2 The primary way liquids and gases transmit heat
is by the process of

• F reflection
• G conduction
• H radiation
• J convection

Fluid heat movement is convection. Fluid motion
occurs in liquids and gases.
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50 A solar heater uses energy from the sun to
heat water. The heaters panel is painted black
to
Convection is movement of heat in fluid matter,
heat loss would be from a solid exterior Not G

• F improve emission of infrared radiation
• G reduce the heat loss by convection currents
• H improve absorption of infrared radiation
• J reduce the heaters conducting properties

Painting a substance will not change its
conductivity That is a property of metals. It
would have to be made of a different substance to
change that Not J
Emission is giving off we want to absorb Not F
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Heat moves by conduction in solids since the
particles are close together and vibrate. . .

• 43 Heat convection occurs in gases and liquids.
  Heat convection does not occur in solids because
  solids are unable to
• A absorb heat by vibrating
• B transfer heat by fluid motion
• C emit radiation by reflecting light
• D exchange heat by direct contact

Solids do radiate heat to their surroundings
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Energy Conversion

• Changing from one type of energy to another is
  the basis of all machines, and life processes on
  earth.
• Our main energy use, electricity is converted
  from mechanical energy, nuclear energy or
  chemical energy.
• During conversions, some of the energy is
  converted to heat and it is therefore not a 100
  efficient process.

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All energy on earth comes from the sun, but how
does it get stored?

• 12 Which of the following is an example of solar
  energy being converted into chemical energy?
• F The sun unevenly heating Earths surface
• G Water evaporating and condensing in the water
  cycle
• H Plants producing sugar during the day
• J Lava erupting from volcanoes for many days

Plants store energy as sugar (glucose) which
requires a chemical change from carbon dioxide
and water.
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Two types of Electricity

• Static Electricity is a build-up of charge that
  is discharged all at once, such as lightening
• Current Electricity is when charges move along a
  path from a source, and cause something to
  happen.

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Static Electricity

• When you walk across the Astroturf on the
  football field, you pick up electrons on your
  feet.
• When you touch someone else, you release this
  build-up of charge resulting in a shock.
• That is a static discharge.

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Current Electricity is moving electrons along a
path

• Electrical Potential Difference (v) is measured
  in Volts
• The amount of moving electric charges, Electric
  Current (I), is measured in Amperes
• Resistance or opposition to the movement of the
  energy is called Resistance (R) and is measured
  in ohms.

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Direct Current vs. Alternating Current

• The type of current depends on the source.
• Direct current sources produce a constant supply
  of moving charge.
• Alternating current is produced by moving a coil
  in a magnetic field which causes the charge to
  change direction.

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USE THE FORMULA SHEET!!

• What is the current in a copper wire that has a
  resistance of 2 ohms and is connected to a 9 volt
  electrical source?
• A. 18.0 amps
• B. 11.0 amps
• C. 4.5 amps
• D. 0.22 amp

Ohms Law states V I R 9V I x
2 ohms or 4.5 amps
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Circuits 2 types

• Series circuits are the most simple.
• One (1) path for the current to travel. You can
  trace through every item on the path without
  lifting your pencil or going over a piece twice.
  
• Contains an energy source, a path, and a load
  (something for it to do, like light a lamp)

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Circuits 2 types

• Parallel circuits provide more than one path for
  the current to travel.
• Most circuits are parallel, because when one lamp
  goes out, the others can stay lit.
• May require multiple switches to work each part
  of the circuit.

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Shorthand for circuits these are some of the
symbols used
Resistor Switch Battery Cell Bulb
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• Which switches, if opened, will
• cause the light bulb to stop glowing?

• Q
• R
• H. S
• J. T

It is the only switch in series to both the
battery and light.
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Electric Energy is converted to

• Heat energy in many appliances.
• Light energy, and heat is given off as a waste
  product.
• When energy appears to have been lost it is
  usually given off as heat.
• Remember friction occurs when any 2 substances
  touch each other. Even air resistance is a form
  of friction.

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Making Electricity -- Generator

• Wind turns the propellers, which spins a coil of
  wire.
• Surrounding the wire a very large magnets.
• The magnetic field causes electrons to be
  alternately attracted and repelled, causing them
  to move along a different wire.
• Moving electrons is current.

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Are there other ways to move the wire coil?
Geotheremal use heat from underground to boil
water
Hydroelectric Dam
All of these power plants generate electricity,
name them
Fossil Fuel Plant, burns fossil fuels.
Nuclear Power Plants use radioactive fuel
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Your turn. . .

• 1. The graph shows how the voltage needed to
  maintain a constant current of 1.5 amps through a
  wire conductor varies with the length of the
  wire. If the trend continues, what is the most
  likely voltage needed to maintain a 1.5-amp
  current through 80 meters of the wire?
• F 400 volts
• G 250 volts
• H 18 volts
• J 10 volts

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• 2. Only 10 of the electrical energy operating a
  lightbulb is changed into visible light. Which
  instrument helps identify the energy change
  occurring to most of the remaining 90?
• F Triple-beam balance
• G Thermometer
• H Magnifying glass
• J Prism

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4. In this circuit, how much current flows
through the lightbulb?

• A 0.75 amp
• B 1.50 amps
• C 2.0 amps
• D 3.0 amps

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5. The bulb will light when a current supplied by
at least one 1.5 V battery is available. Which
circuit will fail to light the bulb?
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Your turn!!

• 1. The typical automobiles kinetic energy is
  converted to heat energy when the brakes are
  applied. A braking system that converts kinetic
  energy to electrical energy instead of heat
  energy has been designed. The electrical energy
  can be used later to move the car again. How does
  a system like this benefit the environment?
• F Greater use of solar energy
• G Ability to harness wind energy
• H Decreased use of fossil fuels
• J Use of renewable hydroelectricity

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• 2. The transfer of heat by the movement of air
  currents in Earths atmosphere is an example
• of
• A conduction
• B convection
• C radiation
• D fusion

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• 3. Which of the following would explain why
  this film works with a reduced amount of light?
• A The film reflects long wavelengths of light
  efficiently.
• B Fewer silver halide granules are present in
  the film.
• C The film refracts brighter light.
• D The photochemical reaction can occur in lower
  intensity light.

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• 4. Which of these tools is most useful in
  identifying the wavelengths of visible light?
• F Convex lens
• G Spectroscope
• H Microscope
• J Concave mirror

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5. The diagram shows waves approaching a
barrier. Which pattern will be formed after the
waves pass through the opening in the barrier?
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• 6. A guitar player is seated next to a piano.
  The piano player strikes an E key on the piano.
  The guitarist reports that this causes the E
  string on his guitar to vibrate. What is the name
  of this phenomenon?
• A Polarization
• B Resonance
• C Reflection
• D Diffraction

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And the answers are. . .

• H Reusing heat energy means less heat needed
  from burning in a car that is a fossil fuel,
  gasoline
• B Air currents refers to convection.
• D Photo refers to light, and images are made by
  a chemical reaction on the film.
• G Spectrum waves are measured by a spectroscope.
  
• B The parts of the wave which pass through
  spread out again, and keep the same pattern.
• B Sound moves through particles such as air,
  which when it hits something with the correct
  frequency will begin it vibrating. This is
  resonance.