Mr. Clark Bethpage HS AP Environmental Science Energy Basics Mr. Clark Bethpage 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’s bottom to vibrate faster. The vibrating atoms or molecules then collide with nearby atoms or molecules, causing them to vibrate faster. Eventually, molecules or atoms in the pan’s handle are vibrating so fast it becomes too hot to touch. As the water boils, heat from the hot stove burner and pan radiate into the surrounding air, even though air conducts very little heat. Heating water in the bottom of a pan causes some of the water to vaporize into 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 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. 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.