Energy

ž    Energy is the ability to cause change

—   Sunshine warming up a room

—   Wind moving leaves

—   Heat from burning gasoline to help a car move

Energy of Motion

ž    Things that move can cause change

ž    Kinetic energy is the energy an object has due to its motion

—    If an object isn’t moving, it doesn’t have kinetic energy

ž    Kinetic energy increases as an object moves faster

—    A fastball in baseball has more kinetic energy than a curveball

ž    Kinetic energy increases as the mass of the object increases

—    If you bowl with a volleyball, not as many pins will be knocked down

Energy of Position

ž    An object can have energy even though it is not moving

ž    Potential energy is the energy stored in an object because of its position

—    Ex: An object on top of a building has more potential energy than an object on the ground because it’s higher

ž    Potential energy also depends on mass

—    A bowling ball on top of a building vs. a feather on top of a building

Thermal Energy

ž    Thermal energy is the total value of the kinetic and potential energy in an object

—   Frequently measured as temperature

ž    All objects have thermal energy

ž    You are constantly releasing thermal energy as heat

Chemical Energy

ž    Chemical Energy is the energy stored in chemical bonds

—   When chemical reactions occur, bonds are broken and energy is released

—   Ex:  Burn gasoline à release energy stored in sugars in item

—   Ex:  You digest food à energy stored in food is released for you to use

Light Energy

ž    The type of energy light carries is called radiant energy.

—   As light “hits” something, it transfers energy to that item and increases it’s thermal energy

Electrical Energy

ž    Electrical energy is energy carried by electrical current

—   Comes out of batteries and large sockets

—   Generated at large power plants

—   Easy to transfer into other types of energy

○   Ex:  Your electricity makes your stove work (thermal), a fan turn (kinetic), a light bulb to turn on (light energy)

Nuclear Energy

ž    Nuclear energy is the energy stored in the nucleus of an atom

—   Used to generate electricity at power plants

—   Releasing energy from a nucleus is tough

Review

Law of Conservation of Energy     

ž    Energy cannot be created or destroyed, only transferred

—   Energy from the sun turns into “food” in a plant à Cow eats the plant and uses some of that energy à Shaniqua eats a hamburger and gets some energy àShaniqua pushes Arnold and gives energy to him à Arnold falls down, hits the floor and heats up the floor slightly

Energy Transformations

ž    Energy can be transferred from kinetic to potential and back to kinetic

—   Ex:  You move something up to a height – what to what?

—   That thing drops -  ???

—   Hits a lever and lifts something - ???

—   That thing drops and falls into fire - ???

—   Catches on fire - ???

Machines

ž    Machines transform energy from one form to another

ž    Electrical energy is one of the most common forms with machines

—    Transfers electrical energy to kinetic, chemical, potential, electrical or thermal energy

ž    Cars – turning chemical energy into kinetic, thermal and electrical

ž    You – turn chemical energy into kinetic, etc.

 

Thermal Energy

ž    Thermal energy is not easy to store

—   It diffuses so easily

—   Why does your furnace keep turning on?

ž    Conduction

—   Transfer of heat by direct contact

 

Thermal Energy

ž    Radiation

—    Transfer of heat by electromagnetic waves

—    Ex: Sunlight carries heat, microwaves

ž    Convection

—    The transfer of thermal energy by the movement of molecules from one part of a material to another

—    Ex: when you boil water, you first heat up the bottom and then the heat spreads throughout

Generating Electricity

ž    A generator is a device that transforms kinetic energy into electrical energy

ž    Power plants generally use a turbine

—    A machine with fan blades that rotate a shaft in the generator to produce electrical energy

How do you turn the turbine?

ž    Boil water and make stream

—   Burn fossil fuels, nuclear energy, geothermal energy

ž    Make a dam and falling water will turn it

ž    Windmills can directly turn it

Sources of Energy

ž    Two sources:

—   The Sun

—   Radioactive atoms in the Earth

 

Fossil Fuels

ž    Oil, natural gas, coal

ž    Fossil fuels come from the remains of dead plants

—    Those plants performed photosynthesis once upon a time and turned the sun’s radiant energy into chemical energy

ž    Fossil fuels are nonrenewable sources

—    Things that are used up faster than they can be replaced

ž    So what happens when we run out??

 

Nuclear Energy

ž    You could use 1 kg of uranium to make an automobile go 90 million miles

ž    Nuclear energy comes from the nuclei of uranium atoms

ž    Energy is used to boil water and turn a turbine

—   Very little waste

—   Very dangerous waste

Renewable Resources

ž    A renewable resource is an energy source that is replenished continually

ž    Hydroelectricity

—    Make a dam

—    Let the water run downhill to turn turbine

—    Very clean resource

—    Disrupts habitats when you dam a river

Alternative Sources of Energy

ž    Alternative resources are new sources of energy that are safer and cause less harm to the environment

—   Solar – an inexhaustible source (we can’t use it up) collected in thermal collectors of photovoltaic collectors

 

Alternative Sources of Energy

ž    Geothermal Energy – thermal energy contained in hot magma and stored in “reservoirs” below the surface

—   Wells drilled to tap into the hot water/steam created

ž    Windmills – another inexhaustible supply where wind turns rotors of a windmill, which turns a turbine

Alternative Sources of Energy

ž    Energy from oceans

—   As waves go up and down, it’s possible to have large flotation devices connected to a turbine.  As float goes up and down, turbine turns

—   As tide comes in and then out, water could turn a turbine

Conserving Energy

ž    If we conserve energy, it will help prevent shortages and will allow fossil fuels to last longer

ž    What can I do?

—    Walk

—    Ride the bus or Trax

—    Use energy efficient light bulbs and appliances

—    Turn off the lights

—    Weatherize your house

—    Recycle

Energy & Waves

ž    Energy is transferred via waves

ž    Waves are disturbances that transfer energy from one place to another

Mediums

ž    A medium is any substance that a wave moves through

—   Ex:  water is a medium for an ocean wave

—   What is the medium for an earthquake wave?

ž    Mechanical waves – waves that transfer energy through matter

—   Most waves are mechanical waves

Types of Waves

ž    Transverse Waves

—   The direction in which the wave travels is perpendicular, or at right angles , to the direction of the disturbance

ž    Longitudinal Waves

—   The wave travels in the same direction as the disturbance

Measuring Waves

ž    Crest – highest point, or peak, of a wave

ž    Trough – lowest point, or valley, of a wave

 

Measuring Waves

ž    Amplitude – the distance above the middle of a wave

—    Indicates how much energy a wave is carrying

ž    Wavelength – the distance from one wave crest to the next wave crest

ž    Frequency – the number of wavelengths passing a fixed point in a certain amount of time

Frequency & Wavelength

ž    When frequency increases, more wave crests pass a fixed point each second

—   So the wavelength shortens

—   The reverse is true also

Sound

ž    Amplitude = Volume

—   High amplitude, loud volume

ž    Frequency = pitch

—   High frequency, high pitch

—   Low frequency, low pitch

ž    Sound travels better through certain mediums

Electromagnetic Waves

ž    Not mechanical waves – don’t need matter

ž    Radio waves

ž    Microwaves

ž    Infrared Light

ž    Ultraviolet Light

ž    Visible Light

ž    X-rays

ž    Gamma rays

Visible Light

ž     Wavelength determines color

—    White light – all visible light

ž     Polarization – a way of filtering light by wavelength

ž     Prisms – refracts light to show all wavelengths

ž     Scattering – spreading of light rays in all directions

—    Because particles in the air reflect and absorb the light

—    It’s what makes the sky blue  - the air scatters blue wavelengths more than any other color