Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
52 Cards in this Set
- Front
- Back
|
Energy Definition |
The capacity to do work |
|
|
Work Definition |
A force applied over distance |
|
|
Equations for work |
w=f/d w= work (lowercase), measured in Joules f= force, measured in Newtons d= distance, measured in meters |
|
|
Where does energy come from? |
The sun |
|
|
How does it travel? |
Energy pathways |
|
|
How does the sun's energy get stored in a book lifted two meters off the ground? |
Sun -> photosynthesis -> digest food -> cellular respiration -> movement -> in the book |
|
|
Energy pathway example warmth/light from a fire |
Sun -> photosynthesis -> combustion -> hot air -> warms skin -> warms blood -> blood flows faster |
|
|
Why do energy pathways work? (law of conservation of energy) |
Energy cannot be created, energy cannot be destroyed, energy can be transformed. |
|
|
Two major energy classifications |
Kinetic energy and potential energy |
|
|
Define kinetic energy |
Energy in a moving object, it often results in energy being stored |
|
|
What is an objects KE a function of? |
It's mass and it's velocity (speed in reality |
|
|
Difference between speed and velocity |
Speed is a part of velocity which is rate and direction |
|
|
To calculate KE |
KE= 1/2(m)(v2) v to the second power is the first step 1/2=constant m=mass (kg) v=velocity (speed m/s) |
|
|
Define potential energy |
Energy stored in an object often due to motion |
|
|
Examples of EPE |
stretch rubber band, amount of energy stored is a result of work done to stretch the rubber band (EPE) |
|
|
To calculate EPE |
EPE=fd |
|
|
Example of GPE |
lift and object; energy stored is a result of raising the object to the height |
|
|
To calculate GPE |
ma(sub g)h =GPE OR mgh=gpe m=mass (kg) ag=gravitational accelleration (9.8 m/s2) h=height (cm) unita for GPE= J(oules) |
|
|
As GPE increases KE decreases As KE increases GPE increases |
Reversible Energy |
|
|
Ex. of reversible energy
|
Pendelum |
|
|
Define solar energy |
Radiant energy (moving photons) from the sun |
|
|
Solar Energy can be converted into what three things? |
1. Chemical energy-photosynthesis 2. Heat 3. Electricity This is a multi-step process |
|
|
General uses of solar-> heat energy first use |
A. to heat water for home or building or swimming pool use 1. Solar thermal collectors a. passive=air/water moves due to heating (convection), no fans, etc. used Think of a car heating up on a hot day, warm sunshine through a window, or solar showers used in backpacking, pool covers dark with sunshine b. active= collectors absorb energy and fans or pumps circulate the warmth Collectros can be concentrating or non-concentrating |
|
|
General uses of solar-> heat energy second use |
B. Heat spaces->greenhouses, homes, buildings See number one (they also have passive and active uses) - Windows face south |
|
|
General uses of solar-> heat energy third use |
C. Heat fluids= to operate turbines to generate electricity 1. parabolic trough- curved mirror set-up that concentrates energy to one point, increases intensity by 30 to 100 times can reach temps of 750 degrees Farenheight 2. Solar dish- a curved, mirror dish that concentrates energy to a single focal point can get u to 1380 degrees Faranheight 3. Solar Power Tower- A single collecting tower at the center of a field of flat reflecting mirrors, can increase energy by 1500X's
|
|
|
Use of three solar devices |
Heat fluids to create steam to turn a turbine to produce electricity |
|
|
Photovoltaic Cells |
Known as solar cells, change sun energy into electricity |
|
|
Everyday use examples of solar cells part 1 |
calculators, watches, etc. |
|
|
solar energy->electricity part 2 |
Individual cells are grouped onto panels to produce larger quantities of electricity; panels can group into large arrays (many panels) to produce even larger quantities of electricity |
|
|
Advantages of Solar energy to electricity |
1. No mechanical generators needed 2. easy to install 3. minimum environmental impact- no water for cooling, no CO2 or other emissions |
|
|
Example of solar energy to electricity part 3 |
Generate DC current that must be converted to AC for transmission |
|
|
Benefits of Solar |
1. do not produce air pollution 2. usually do not require water based cooling systems 3. once installed inexpensive to operate |
|
|
Limitations of Solar |
1. Sunlight reaching earth's surface is not constant, it depends on time of day, time of year, weather 2. Sun energy needs to be concentrated, can require large surface areas to collect enough to be useful (can take up a lot of space) 3. Cost of initial installation of equipment |
|
|
Electricity |
- Energy from moving electrons - Most used in the U.S BECAUSE; a. easily produced as fossil fuels, wood, hydro, nuclear, geothermal, wind, solar b. Relatively inexpensive c. easy to TRANSFORM* into heat, sound, radiant, mechanical d. easy to transmit long distances e. Relatively safe f. easy to store g. relatively clean (not necessarily to produce) |
|
|
Electricity Transmission |
1. Produced at a power plant 2. transferred via high voltage power lines (60,000 gonna lose energy) 3. Transformers reduce the voltage to levels that can be used in a home (can also transform voltage) 4. Electricity travels in circuits in the house- designed to carry specific levels (amps) of electricity 5. Safety devices to prevent overflows a. fuses- with a wire that melts and breakers b. circuit breakers-switch that opens |
|
|
Electric Consumption |
- How much energy is used - NOT CALLED ELECTRIC POWER - Power=rate energy is used P=w/t w=work (Joules) lowercase t=time (seconds) p=power (J/s) - Every device uses energy at a rate |
|
|
How many watts is 1J/s using |
1 watt (1 W) |
|
|
A 60 watt lightbulb uses |
60J/s |
|
|
Electric Consumption depends on |
1. how long something is used (time) 2. Amount of J (energy) needed to operate the device |
|
|
Energy equation |
P=w/t OR p*t=w |
|
|
Given: 1500 W oven 3 hr to cook How many Joules are used? |
p=w/t 1500W=w/3hr 1500W*3hr=w 4500W=amount of Wh (Watt hours) 4500wh/1000wh=4.5 KWH- kilowatt hours, use this |
|
|
Definition of Wind Energy |
A form of solar energy describing the process of wind generating mechanical power or electricity |
|
|
What are winds caused by? |
The uneven heating of the atmosphere by the sun, irregularities of earth's surface, rotation of the earth |
|
|
Energy pathway for wind |
solar->thermal->wind *It is kinetic energy* |
|
|
Early uses of wind energy |
- First used in 5000 B.C. as sailing ships in Egypt - 2000 B.C was used to grind grains 900 B.C. Persians grinded grains 900-500 B.C China pumped water from the ground - Dutch used wind to drain wetlands 9used windmills) in 1,000 A.D - Still pump water in U.S - Used in western U.S since 1800's |
|
|
Describe modern windmill |
-200-300 ft tall - 200 ft blades - Have a turbine that creates electricity |
|
|
Potential Power Output |
- 5% of US energy is from wind - 5%=70 gigawatts - 5% powers 18,000,000 homes (18 million) - 40% of Texas and 66% of power in Colorado is from wind - One large turbine= 600 homes |
|
|
Location of wind power |
Germany, Spain, Us, India, Denmark - US leads world in wind energy production |
|
|
Economic advantages wind power |
1. Fuel is free 2. Low maintenance cost 3. Low operation cost 4. Independence from foreign fuels 5. Jobs |
|
|
Economic disadvantages wind power |
1. Expensive to install 2. Takes up land 3. Need wind so it's dependent on the weather 4. Damage during construction |
|
|
Environmental Advantages |
- Minimum carbon footprint - No other air pollution - Renewable energy - Doesn't use water (flexible) doesn't have to be near river |
|
|
Environmental disadvantages |
1. Construction= erosion 2. Makes things look ugly (aesthetics) 3. Kills wildlife 4. Noisy |
