energy basics mr. clark bethpage hs ap environmental science
TRANSCRIPT
Energy Basics
Mr. ClarkBethpage HS
AP Environmental Science
Energy Basics
Energy Work Power First Law of Thermodynamics Second Law of Thermodynamics Kinetic energy Potential energy
Energy Basics
First Law Efficiencies Second Law Efficiencies Thermal efficiency Electrical resistivity Conservation The hard path versus the soft path
Energy
Energy is the ability to do work. Energy is measured in units called Joules.
Energy is also measured in calories, BTUs, and ergs.
Electromagnetic Spectrum
Transfer of Energy
Convection Conduction Radiation
Heat from a stove burner causes atoms or molecules in the pan’sbottom to vibrate faster. The vibrating atoms or molecules then collide withnearby atoms or molecules, causingthem to vibrate faster. Eventually, molecules or atoms in the pan’shandle are vibrating so fast itbecomes too hot to touch.
As the water boils, heat from the hot stove burner and pan radiate into thesurrounding air, even though airconducts very little heat.
Heating water in the bottom of a pancauses some of the water to vaporizeinto bubbles. Because they are lighter than the surrounding water, they rise. Water then sinks from the top to replace the rising bubbles.This up and down movement (convection) eventually heats all of the water.
Energy Quality
Work
Work is force times distance. W = F x d The unit of work is a Newton-meter.
A Newton-meter is called a Joule (J).
Power Power is the rate that energy is used. Power is equal to work / time. P = W/t One joule / second is a watt. Electrical Power can also be calculated
by another formula. Electrical Power = voltage x current. P = V x I watts = volts x amps
First Law of Thermodynamics
Energy is neither created nor destroyed but is always conserved and transformed from one kind to another.
Energy only changes form. You cannot get something from
nothing. Energy in = energy out
Second Law of Thermodynamics
Energy always goes from a more usable form (high quality) to a less usable form. (low quality)
All systems move to maximum entropy.
Kinetic Energy
Kinetic energy is the energy of motion.
KE = ½ mv2 where m is mass and v is velocity.
Potential Energy
Potential energy is stored energy. PE = m x g x h where m is mass, g
is the acceleration due to gravity, and h is height.
First Law Efficiencies
First Law Efficiencies are the amount of energy available without consideration of energy quality.
Second Law Efficiencies
Second Law Efficiencies are the amount of energy available with consideration of energy quality.
Thermal efficiency
Thermal efficiency is the maximum possible efficiency of a heat engine. (Carnot 1824)
Electrical resistivity
Electrical resistivity is what causes electrical energy to be converted to heat energy.
It is like electrical friction.
Conservation
Conservation is saving energy whenever possible.
The hard path vs. the soft path
Hard Path Let energy companies
develop resources. Do away with
regulations so that the market can determine the most efficient use of energy with the least environmental consequences.
Soft Path Develop alternate
energy technologies such as solar, wind, and biomass.
Use diverse technologies.
Be flexible with the use of technologies.
Match the needs of the area.