mechanical thermal chemical nuclear electrical radiant types of energy table of contents

•Mechanical•Thermal•Chemical•Nuclear•Electrical•Radiant

Types of Energy

Table of ContentsTable of Contents

Mechanical Energy Review• ME = PE + KE

• KE = ½ m v2

greatest at position 2

• GPE = mgh

greatest at position 1 and 5

4

Thermal Energy The sum of the kinetic and potential energy of

all the particles in an object is the thermal energy of the object.

6.16.1

Matter in Motion • The faster they move, the more kinetic

energy they have.

• This figure shows that particles move faster in hot objects than in cooler objects.

6.16.1Temperature and HeatTemperature and Heat

Transfer Thermal Energy

• Thermal energy is transferred when one end of a metal spoon is heated by a Bunsen burner.

• The kinetic energy of the particles near the flame increases.

6.26.2Transferring Thermal EnergyTransferring Thermal Energy

• Kinetic energy is transferred when these particles collide with neighboring particles.


• As these collisions continue, thermal energy is transferred from one end of the spoon to the other end of the spoon.

Transfer Thermal Energy

Radiant Energy and Matter

• Different materials on Earth absorb radiation in different amounts resulting in uneven heating.

• Sea breezes and Land breezes are examples of this.

• Natural convection currents are created.


Internal Combustion Engines• A car engine is an internal combustion engine

6.36.3Using HeatUsing Heat

• Each cylinder contains a piston that moves up and down (a stroke).

• The heated material in the cylinders expands forcing the piston down.

• As exhaust gases are released, the piston comes up.

• As the crankshaft moves with the piston, it turns vital parts of the car.

Internal Combustion Engines6.36.3

Using HeatUsing Heat

• Chemical energy comes from energy release when chemical bonds are broken or formed.

• When we eat, we break the bonds in our food to release energy to be used by our body.

• Same goes for chemical fuel used for other reasons.

Chemical Energy

• Compared to other fuels such as wood, the chemical energy that is stored in fossil fuels is more concentrated.

• For example, burning 1 kg of coal releases two to three times as much energy as burning 1 kg of wood.

Chemical Energy Sources9.19.1

• Petroleum is a highly flammable liquid formed by decayed ancient organisms, such as microscopic plankton and algae.

• It is one of the fossil fuels.

• The key ingredient to fossil fuel

is a carbon hydrogen bond

called a hydrocarbon.

Carbon is found in all living and once living things.

Petroleum9.19.1Fossil FuelsFossil Fuels

9.29.2 Nuclear Energy• Nuclear Energy is a type of chemical energy

• A nuclear power plant generates electricity using the energy released in nuclear fission.

• The sun generates energy

transferred as light

by nuclear fusion.

9.29.2Nuclear Fission

When a neutron strikes the nucleus of a U-235 atom, the nucleus splits apart into two smaller nuclei.

In the process-two or three neutrons are emitted,-smaller nuclei are called fission products of barium and krypton are created,-and energy is released

.

9.29.2Nuclear Fusion

Thermonuclear fusion is the joining together of small nuclei at high temperatures.

•2 hydrogen atoms fuse to form a helium atom of less mass

•The mass lost turns into energy by E=mc2

• Atoms contain particles called protons, neutrons, and electrons.

• Protons are positively charged

• Electrons have a negative charge,

• Neutrons have no electric charge.

Electrical Energy 7.17.1

• When you walk on the carpet, electrons are transferred from the carpet to the soles of your shoes.

Static Electricity 7.17.1

Electric ChargeElectric Charge

• Your shoe soles become negatively charged. • The carpet lost electrons and is positively

charge. • The accumulation of excess electric charge

on an object is called static electricity.

• Lightning is a large static discharge.

Lightning 7.17.1

Static ChargeStatic Charge

• A static discharge is a transfer of charge between two objects

• A thundercloud is a mighty generator of static electricity. As air masses move and swirl in the cloud, areas of positive and negative charge build up.

• Eventually, enough charge builds up to cause a static discharge between the cloud and the ground.

Lightning 7.17.1

Static ChargeStatic Charge

• As the electric charges move through the air, they collide with atoms and molecules. These collisions cause the atoms and molecules in air to emit light.

Current and Voltage Difference

• The net movement of electric charges in a single direction is an electric current.

7.27.2Electric CurrentElectric Current

• When an electric current flows in the wire, electrons drift in the direction that the current flows.

• Electric current is measured in amperes (Amps).

Voltage Difference

• Electric charge flows from higher voltage to lower voltage.

• A voltage difference is related to the force that causes electric charges to flow. Voltage difference is measured in volts.


• Law of conservation of charge, charge can be transferred, but it cannot be created or destroyed.

• Whenever an object becomes charged, electric charges have moved from one place to another.

Conservation of Charge 7.17.1


• A material in which electrons are able to move easily is a conductor.

Conductors7.17.1


• The best electrical conductors are metals.

• The atoms in metals have electrons that are able to move easily through the material.

• A material in which electrons are not able to move easily is an insulator.

Insulators7.17.1


• Electrons are held tightly to atoms in insulators.

• Most plastics are insulators. • The plastic coating

around electric wires prevents a dangerous electric shock when you touch the wire.

Electric Circuits 7.27.2

Electric CurrentElectric Current

• A closed path that electric current follows is a circuit.

• If the circuit is broken by removing the battery, or the light bulb, or one of the wires, current will not flow.

Resisting the Flow of Current

• Resistance is the tendency for a material to oppose the flow of electrons, changing electrical energy into thermal energy and light.


• Resistance is measured in ohms ().

• Depends on temperature, length, and diameter: hotter, longer, thinner increases resistance

Ohm's Law 7.27.2

Electric CurrentElectric Current

• According to Ohm's law, the current in a circuit equals the voltage difference divided by the resistance.

• The voltage difference, resistance, and current in a circuit are related.

• Ohm's law provides a way to measure the resistance of objects and materials. First the equation above is written as: I = V/R

Series Circuits

• One kind of circuit is called a series circuit.

• In a series circuit, the current has only one loop to flow through.

7.37.3Electrical EnergyElectrical Energy

• Series circuits are used in flashlights and some holiday lights.

Parallel Circuits

• Houses are wired with parallel circuits.


• Parallel circuits contain two or more branches for current to move through.

• The current can flow through both or either of the branches.

Household Circuits • The main switch and circuit breaker or fuse

box serve as an electrical headquarters for your home.


• Parallel circuits branch out from the box to wall sockets, major appliances, and lights.

Household Circuits 7.37.3

Electrical EnergyElectrical Energy

• To protect against overheating of the wires, all household circuits contain either a fuse or a circuit breaker.

• The rate at which electrical energy is converted to another form of energy is the electric power.

Magnetic Domains8.18.1

MagnetismMagnetism

• Magnetic material contains domains of enormous number of atoms that align their charges.

• Domains are also aligned creating a magnetic field with polar ends.

• A magnetic field exerts a force on other magnets and objects made of magnetic materials.

Magnetic Field 8.18.1

MagnetismMagnetism

• The magnetic field is strongest close to the magnet and weaker far away.

• The field also has direction.

• Magnetic poles are where the magnetic force exerted by the magnet is strongest.

Magnetic Poles 8.18.1

MagnetismMagnetism

• Like poles (ie.2 north poles or 2 south poles) repel each other.

• Opposite poles (ie. north poles and south poles) attract each other.

Earth’s Magnetic Field8.18.1MagnetismMagnetism

The earth is a large magnet due to a solid inner core of iron and nickel surrounded by a spinning layer of liquid iron and nickel.

• A compass can help determine direction because the north pole of the compass needle points to the northern geographic pole which is actually a south magnet pole.

Earth’s Magnetic Field8.18.1MagnetismMagnetism

Moving Charges and Magnetic Fields

• It is now known that moving charges, like those in an electric current, produce magnetic fields.

• Around a current-carrying wire the magnetic field lines form circles.

8.28.2Electricity and MagnetismElectricity and Magnetism

Electromagnets

• A single wire wrapped into a cylindrical wire coil is called a solenoid.


• An electromagnet is a temporary magnet made by wrapping a wire coil carrying a current around an iron core.

• The magnetic field inside the loop is stronger than the field around a straight wire.

• Step 1. When a current flows in the coil, the magnetic forces between the permanent magnet and the coil cause the coil to rotate.


• An electric motor is a device that changes electrical energy into mechanical energy.

Electric Motors

Making the Motor Spin • Step 2. In this position, the brushes are not in

contact with the commutator and no current flows in the coil.


• The inertia of the coil keeps it rotating.

Making the Motor Spin

• Step 3. The commutator reverses the direction of the current in the coil.


• This flips the north and south poles of the magnetic field around the coil.

Making the Motor Spin

• Step 4. The coil rotates until its poles are opposite the poles of the permanent magnet.


• The commutator reverses the current, and the coil keeps rotating.

Generators• A generator uses electromagnetic

induction to transform mechanical energy into electrical energy.

• In this type of generator, a current is produced in the coil as the coil rotates between the poles of a permanent magnet.

8.38.3Producing Electric CurrentProducing Electric Current

Generating Electricity for Homes8.38.3

Producing Electric CurrentProducing Electric Current

The rotating magnets are connected to a turbine, a large wheel that rotates when pushed by water, wind, or steam.

Direct and Alternating Currents 8.38.3


• A battery produces a direct current.

• Direct current (DC) flows only in one direction through a wire.

• Power companies produce alternating current (AC) reverses the direction of the current in a regular pattern.

Transmitting Electrical Energy 8.38.3


• When the electric energy is transmitted along power lines, some of the electrical energy is converted into heat due to the electrical resistance of the wires.

• The electrical resistance and heat production increases as the wires get longer.

Transmitting Electrical Energy 8.38.3


• One way to reduce the heat produced in a power line is to transmit the electrical energy at high voltages, typically around 150,000 V.

• Electrical energy at such high voltage cannot enter your home safely, nor can it be used in home appliances.

• A transformer is used to decrease the voltage.

Transformers 8.38.3


• A transformer is a device that increases or decreases the voltage of an alternating current.

• A transformer is made of a primary coil and a secondary coil.

• These wire coils are wrapped around the same iron core.

Transformers 8.38.3


A transformer that increases the voltage so that the output voltage is greater than the input voltage. • A transformer that

decreases the voltage so that the output voltage is less than the input voltage.

Transmitting Alternating Current 8.38.3


• This figure shows how step-up and step-down transformers are used in transmitting electrical energy from power plants to your home.

• A wave is a repeating disturbance or movement that transfers energy through matter or space.

10.110.1The Nature of Waves The Nature of Waves

• The waves don’t carry matter along with them. Only the energy carried by the waves moves forward.

• A wave will travel only as long as it has energy to carry.

Mechanical Waves

• Mechanical waves are waves that travel through matter.

• The matter the waves travel through is called a medium.

• The medium can be a solid, a liquid, a gas, or a combination of these.

10.110.1The Nature of Waves The Nature of Waves

• A transverse wave moves up and down.

10.110.1Types of Mechanical of Waves Types of Mechanical of Waves

• A compressional wave moves back and forth.

Water Waves a mechanical wave of a combination of transverse and compression action.

10.110.1Examples of Mechanical Waves Examples of Mechanical Waves

Seismic Waves are also a combination of both actions that go through the Earth’s crust

The Parts of a Wave

• A transverse wave has alternating high points, called crests, and low points, called troughs.

10.210.2Wave PropertiesWave Properties

Wavelength • A wavelength is the distance between one

point on a wave and the nearest point just like it.

• For transverse waves the wavelength is the distance from crest to crest or trough to trough.


Frequency and Period

• The frequency of a wave is the number of wavelengths that pass a fixed point each second.

• You can find the frequency of a transverse wave by counting the number of crests or troughs that pass by a point each second.


• Frequency is expressed in hertz (Hz).

Calculating Wave Speed

• You can calculate the speed of a wave represented by v by multiplying its frequency times its wavelength.


Amplitude of Transverse Waves 10.210.2

Wave PropertiesWave Properties

• The amplitude of any transverse wave is the distance from the crest or trough of the wave to the rest position of the medium.

The Law of Reflection

• The beam striking the mirror is called the incident beam.

10.310.3The Behavior of Waves The Behavior of Waves

• The beam that bounces off the mirror is called the reflected beam.

Refraction

• Refraction is the bending of a wave caused by a change in its speed as it moves from one medium to another.


Diffraction

• Waves also can be diffracted when they pass through a narrow opening.


• After they pass through the opening, the waves spread out and bend.

Interference • When two or more

waves overlap and combine to form a new wave, the process is called interference. Interference occurs while two waves are overlapping.


Constructive Interference • In constructive interference, the waves

add together.


• The amplitude of the new wave that forms is equal to the sum of the amplitudes of the original waves.

Destructive Interference

• In destructive interference, the waves subtract from each other as they overlap.


• This happens when the crests of one transverse wave meet the troughs of another transverse wave.

• Electromagnetic waves are made by vibrating electric charges and can travel through space where matter is not present.

• Instead of transferring energy from particle to particle, electromagnetic waves travel by transferring energy between vibrating electric and magnetic fields.

Electromagnetic Waves12.112.1What are electromagnetic waves?What are electromagnetic waves?

• All electromagnetic waves travel at 300,000 km/s in the vacuum of space.

• The speed of electromagnetic waves in space is usually called the “speed of light.”

Wave Speed12.112.1What are electromagnetic waves?What are electromagnetic waves?

• As the frequency increases, the wavelength becomes smaller.

• Energy carried by a wave depends on its amplitude and not its frequency.

Waves and Particles12.112.1What are electromagnetic waves?What are electromagnetic waves?

• Albert Einstein stated electromagnetic waves can behave as a particle, called a photon, whose energy depends on the frequency of the waves.

A Range of Frequencies • Electromagnetic waves can have a wide

variety of frequencies. • The entire range of electromagnetic wave

frequencies is known as the electromagnetic spectrum.

12.212.2The Electromagnetic SpectrumThe Electromagnetic Spectrum

Visible Light• Visible light is the range of electromagnetic

waves that you can detect with your eyes. • Visible light has wavelengths around 750

billionths to 400 billionths of a meter.

12.212.2The Electromagnetic SpectrumThe Electromagnetic Spectrum

Radiant Energy and Light

The Behavior of LightThe Behavior of Light

13.113.1

•Light is the result of radiant energy traveling in electromagnetic waves that hit materials and excite the material’s electrons.

•Those electrons move farther away from the nucleus

• When it returns the electron gives off photons of electromagnetic waves.

The Law of Reflection

• Because light behaves as a wave, it obeys the law of reflection.

• According to the law of reflection, light is reflected so that the angle of incidence always equals the angle of reflection.


13.113.1

Colors• An object’s color depends on the wavelengths

of light it reflects.

13.213.2

• You know that white light is a blend of all colors of visible light.

• This image shows white light striking a green leaf. Only the green light is reflected to your eyes.

Light and ColorLight and Color

Refraction and Rainbows

• Like prisms, rain droplets also refract light.


• The refraction of the different wavelengths can cause white light from the Sun to separate into the individual colors of visible light.

13.113.1

• Refraction is caused by a change in the speed of a wave when it passes from one material to another.

Light and the Eye• In a healthy eye, light enters and is focused on

the retina, an area on the inside of your eyeball.

13.213.2

• The retina is made up of two types of cells that absorb light.


• These cells absorb light energy, chemical reactions convert light energy into nerve impulses that are transmitted to the brain.

Light and the Eye13.213.2

• One type of cell in the retina, called a cone, allows you to distinguish colors and detailed shapes of objects and are most effective in daytime vision.


• The second type of cell, called a rod, is sensitive to dim light and is useful for night vision.

• Red, green, and blue are the primary colors of light. When mixed together in equal amounts they produce white light.

Mixing Colors

• A pigment is a colored material that is used to change the color of other substances.

13.213.2

• The color of a pigment results from the different wavelengths of light that the pigment reflects.


• A primary pigment’s color depends on the color of light it reflects.

• If all the primary light colors are reflected in equal amounts, the object appears white.

• The image formed when an object is placed by a mirror changes depending on its position in relation to the mirror’s focal point.

Mirrors14.114.1MirrorsMirrors

•The mirrors are often used to magnify objects.

• If the surface of a mirror is curved inward, it is called a concave mirror.

• A mirror that curves outward like the back of a spoon is called a convex mirror.

Convex Mirrors14.114.1MirrorsMirrors

• Objects tend to appear smaller and farther away such as in rear view and side mirrors of cars.

What is a lens? • A lens is a transparent material with at least

one curved surface that causes light rays to bend, or refract, as they pass through.

• The image that a lens forms depends on the shape of the lens.

• Like curved mirrors, a lens can be convex or concave.

14.214.2LensesLenses

• The type of image a lens forms depends on where the object is relative to the focal point.

Convex Lenses

• A convex lens is thicker in the middle than at the edges.


• When the candle is more than two focal lengths away from the lens, its image is real, reduced, and upside down.

Concave Lenses• A concave lens is thinner in the middle and

thicker at the edges.


• The image is always virtual, upright, and smaller than the actual object is.

Focusing on Near and Far

• As an object gets farther from your eye, the focal length of the lens has to increase.


• The muscles around the lens stretch it so it has a less convex shape.

Focusing on Near and Far14.214.2

LensesLenses

• But when you focus on a nearby object, these muscles make the lens more curved, causing the focal length to decrease.

Vision Problems—Farsightedness• If you can see distant objects clearly but can’t

bring nearby objects into focus, then you are farsighted.


Farsightedness• To correct the problem, convex lenses cause

incoming light rays to converge before they enter the eye.


Astigmatism

• Another vision problem, called astigmatism occurs when the surface of the cornea is curved unevenly.


• When people have astigmatism, their corneas are more oval than round in shape.

• Astigmatism causes blurry vision at all distances.

Nearsightedness• If you have nearsighted friends, you know

that they can see clearly only when objects are nearby.


• When a nearsighted person looks at distant objects, the light rays from the objects are focused in front of the retina.

Nearsightedness• A concave lens in front of a nearsighted eye

will diverge the light rays so they are focused on the retina.


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