Forms of Energy
Energyis the ability to do work.It is one of the fundamental building blocks of the universe.
Since energy is the ability to do work, and work is the product of a force over the distance it acts, energy can be understood asthe ability to cause a force to act over a certain distance.
Energy is a necessary component of everything in the universe.Every event that takes place, from the formation of stars to the operation of machines, involves energy that is flowing from one place to another and changing back and forth from one form to another.Energy flows via waves.The different forms of energy include:
· kinetic
· potential
· mechanical
· radiant (light)
· thermal
· sound
· electrical
In some ways, kinetic and potential energy can be thought of as the two fundamental types of energy.Kinetic energyis the energy of motion, and potential energyis stored energy.All other forms of energy contain aspects of kinetic and/or potential energy.
Kinetic Energy
Kinetic energy is the energy that an object has due to its motion.Kinetic energy is present in all moving objects such as:
· a moving car
· a sliding sled
· a moving ball
· blowing wind
· flowing water
· a spinning amusement park ride
All moving objects have kinetic energy.
Kinetic energy can be harnessed and transformed into other kinds of energy. Humans routinely transform kinetic energy into electrical energy by using the energy of flowing water in hydroelectric dams, blowing wind in wind turbines, and rising steam in other power plants.
The amount of kinetic energy an object has is related to its mass and velocity. The greater the velocity and mass of an object, the more kinetic energy it has.For example, if a car, a van, and a bus were moving at the same speed, the bus would have the most kinetic energy because it has the most mass.
Potential Energy
Potential energy is defined as stored energy.Energy is stored by doing work against a force.Potential energy comes in many different forms including:
· elastic potential energy
· gravitational potential energy
· chemical potential energy
Potential energy that results from stretching or compressing an object is called elastic potential energy.For example, when a spring is stretched, work has been done to deform the spring, resulting in increased potential energy.When the spring is released, the potential energy will be transformed to kinetic energy as the spring snaps back into its original shape.This is also true of a spring that is compressed.
Stretched or compressed objects store elastic potential energy.
Potential energy that is related to an object's height above the ground is known asgravitational potential energy.Generally, an object's gravitational potential energy is directly proportional to the object's mass, height, and the acceleration due to gravity.When two object's masses are equal, the object with the greater height has the greater gravitational potential energy.
The bungee jumper in this picture has gravitational potential energy due to his height.As he falls, it is transformed into kinetic energy.
Chemical potential energyis the energy that is stored in the bonds and attractions within and between the atoms that make up molecules.When a substance undergoes a chemical reaction, chemical potential energy is released.
Chemical potential energy is the type of energy that humans and other organisms get out of food.The food we eat contains stored chemical energy, and oxidation of the food through cellular respiration releases this energy for use in our bodies.Different substances contain different amounts of chemical energy; in other words, some substances are more likely than others to undergo chemical changes.
Substances that can be burned, such as fossil fuels and wood, also contain chemical potential energy.So when coal, oil, wood, or natural gas are burned, their chemical potential energy is released.
Substances contain chemical potential energy due to the bonds between their atoms and molecules.Chemical reactions, such as burning, can release this energy.
Hydrogen fuel and batteries also contain chemical potential energy.These technologies are often calledenergy carrierssince they can be used to store energy and transport it to new locations.
Mechanical Energy
Mechanical energy is best understood as the sum of an object's kinetic energy and potential energy.So it is the total amount of energy that an object has due to its position, orientation (if it's stretched or compressed), and its motion.
A skateboarder on a ramp, for example, has kinetic energy due to his motion, but he also has gravitational potential energy every time he leaves the ground. Both of these values change as he moves up and down a ramp, but his mechanical energy (potential+kinetic) does not change.
A skateboarder loses kinetic energy and gains potential energy as he moves up a ramp.But his mechanical energy remains constant.Objects with mechanical energy are able to do work, and mechanical energy is the form of energy involved in the operation of simple machines.For example, if a person lifts an axe above his head, he gives the axe potential energy because the axe is now above the ground.The person had to use kinetic energy to lift the axe. As the person brings the axe down, he is still using kinetic energy, and the energy of the axe is changed into kinetic energy because it is now in motion. When the axe strikes a piece of wood, it can transfer some of its energy to the wood, doing work on the wood and causing two portions of wood to move away from each other.
Radiant Energy (Light)
Radiant energy is energy that is transmitted in the form ofelectromagnetic waves.Because of this, radiant energy does not need a medium to travel through.Examples of radiant energy includevisible lightand infrared light, which can come from the Sun.Numerous human-made objects also emit radiant energy, including light bulbs and street lights. Radiant energy is carried by electromagnetic waves. These waves can include visible light, infrared light, x-rays, gamma rays, and radio waves.Humans harness radiant energy from the Sun (solar energy) to generate electricity using solar cells and power stations.
Thermal Energy
Thermal energy is the energy of an object due to the random motion of its particles.The faster the particles move, the greater the thermal energy, and the greater the temperature. Temperature can be used as an indicator of the amount of thermal energy that an object possesses, but it is not the same as thermal energy. Heatis thermal energy that is transferred from warmer objects to colder objects.Heat energy can be produced from matter that undergoes a chemical change or from another form of energy.Heat is an important ingredient in the production of electricity at power plants.It can be used to boil water and produce steam, which can create pressure and cause the blades of a turbine to turn. Steam is water that is in the gaseous state.Since water expands when it changes from a liquid to a gas, it creates pressure that can turn against the fan blades of a turbine and cause the turbine to turn.
Sound Energy
Sound energy is the form of energy that is carried by sound waves as they travel through a medium, such as air.Sound waves are produced by vibrating objects and travel through various materials. The vibrating of a drum produces sound waves that travel through the air.These waves carry sound energy. The speed of a sound wave depends on what the wave is traveling through. Sound travels more quickly through more elastic substances.Water, for example, carries sound waves more rapidly than air.Sound waves cannot travel through a vacuum such as outer space because there is no material for the waves to travel through.
Electrical Energy
Electrical energy is the energy associated with charged particles, such as electrons.When these particles are moving or flowing in acurrent, this kind of energy is also referred to aselectricity.Electricity travels through conducting materials, such as wires.Lightning is an example of electrical energy in nature. Electrical energy is an incredibly useful form of energy because it can be generated from many other types of energy and easily transported to new locations.Once it is generated, electrical energy can be transformed into heat, light, sound, or mechanical energy.For this reason, electricity is sometimes called anenergy carrier.
Electrical energy is the energy associated with charged particles—usually electrons.Humans commonly carry energy over long distances using electricity.Electricity is easily transformed into other forms of energy. Batteries, solar cells, generators, flowing water, moving air, and burning fossil fuels can all be used to produce electrical energy.However, it is important to note that energy cannot be created or destroyed.It only changes form.So the electrical energy produced from any of the sources above originated as a different form of energy somewhere else.
Energy Resources
Numerous natural resources are used by human societies to generate energy (particularly electrical energy).There are many different ways of obtaining, transforming, and distributing this energy, each of which has different environmental consequences.
Fossil Fuels
The most common method for obtaining energy is through the burning of fossil fuels, such as coal, oil, and natural gas.These fuels can be converted to other forms of energy in many ways, including the production of electricity through coal-burning power plants.Fossil fuels are abundant and cheap, and coal-burning power plants are currently the most effective way for generating widespread electricity where and when it is needed.However, coal-fired power plants cause large amounts of pollution and can affect the Earth's natural greenhouse effect.Also, fossil fuels are nonrenewable resources, so humans will eventually run out of them at current rates of usage.
Power plants like this one burn coal in order to produce electricity.While coal is plentiful and cheap, it produces a lot of air pollution.Measures are being taken to reduce the amount of pollution released by coal burning, but it is impossible to completely eliminate it.
Solar Energy
Solar energyis an inexhaustible resource, which means humans cannot use it all up, and it a type ofgreen energy—it has far fewer environmental consequences than fossil fuels.The primary negative effects are minor and are related to the manufacturing and disposing of solar panels, which are used to convert solar energy into electrical energy.The main reason that solar energy technology is not more widespread at this time is that it is very expensive to harness solar energy in useful quantities.Solar energy is also not as reliable as energy derived from fossil fuels, because it is not always sunny.Not all locations can utilize solar technologies either.While California and Colorado might be excellent places for solar power plants, Wisconsin and Michigan might not be.But as the technology continues to improve, solar energy costs decrease, and more solar panels are being used.
Solar energy can be harnessed using solar panels such as this one.While this process results in far less pollution or waste than burning fossil fuels, it is currently very expensive and therefore not yet used widely across the world.
Wind Energy
Wind energyis an inexhaustible resource that comes from the movement of air heated by the Sun.Wind energy is also a form of green energy.As with solar energy, wind energy has very few negative environmental consequences, and these are mostly related to the manufacture and disposal of wind turbines.However, wind turbines also pose hazards for birds and bats. Unlike solar energy technologies, wind technologies are relatively inexpensive. In terms of electricity prices, wind energy is able to compete with fossil-fuel generated electricity, but there are limitations to wind as well.The inconsistency of wind patterns is one of the challenges facing the expansion of wind power.It is not always easy to predict when and where the wind will be blowing.And there is not enough wind in many locations to generate electricity.It is estimated that the U.S. has enough wind to supply about 20% of its current electricity demand, if wind energy is used to its full potential.
Wind turbines like these are used to convert blowing wind energy into electricity.This process offers a much cleaner alternative to burning fossil fuels, but not every location is suitable for wind power.And wind power is unreliable, since the wind does not blow in consistent patterns.
Hydroelectric Energy
Hydroelectric energyis electrical energy converted from the kinetic energy of falling water.It is an inexhaustible resource.Like solar and wind power, hydroelectricity is considered to be a green energy.Humans have constructed dams in many parts of the world to hold back rivers.The held-back water is then released through tunnels in the dam to spin turbines that run generators (see figure below).Hydroelectric energy is much cleaner than fossil fuels, but the construction of dams is extremely disruptive to natural ecosystems, especially where it prevents fish and other aquatic animals from moving up or down a river.Hydroelectric energy can also be harnessed from the motion of tidal waters, but such examples are not as common as those that use river dams.
Diagram of a hydroelectric dam.The main environmental drawback of dams like these is their disruption of river ecosystems.
Energy Transformations
Energy can betransformed, or changed, from one form to another.
Energy can change forms as it travels through an object, material, or system.Types of energy transformations can include:
· change from chemical energy to radiant, acoustic, or electrical energy
· change from kinetic energy to potential energy
· change from nuclear energy to light, chemical, or mechanical energy
· change from almost any other form of energy to heat energy
Energy transformation diagrams are sometimes used to show how energy is changed as it is transferred from place to place.
Transformation of Chemical Energy
Chemical energy is energy that an object or material has because of the bonds, or attractions, holding the particles of the material together.Batteries contain chemical energy.Fossil fuels contain chemical energy that is released when the fuels are burned.Food contains chemical energy that is released by our bodies and used to perform life processes.Some common transformations of chemical energy are shown in the energy transformation diagrams below.