forms of energy

comparing forms of energy

Energy, or the ability to do work, can exist in many different forms. The photo in Figure 17.8 represents six of the eight different forms of energy that are described in this lesson. The guitarist gets the energy he needs to perform from chemical energy in food. He uses mechanical energy to pluck the strings of the guitar. The stage lights use electrical energy and give off both light energy and thermal energy, commonly called heat. The guitar also uses electrical energy, and it produces sound energy when the guitarist plucks the strings. For an introduction to all these forms of energy, go to this URL: . For an interactive animation about the different forms of energy, visit this URL: After you read below about different forms of energy, you can check your knowledge by doing the drag and drop quiz at this URL: .

nuclear energy

The nuclei of atoms are held together by powerful forces. This gives them a tremendous amount of stored energy, called nuclear energy. The energy can be released and used to do work. This happens in nuclear power plants when nuclei fission, or split apart. It also happens in the sun and other stars when nuclei fuse, or join together. Some of the suns energy travels to Earth, where it warms the planet and provides the energy for photosynthesis (see Figure

electrical energy

Electrons are negatively charged particles in atoms. Moving electrons have a form of kinetic energy called electrical energy. If youve ever experienced an electric outage, then you know how hard it is to get by without electrical energy. Most of the electrical energy we use is produced by power plants and arrives in our homes through wires. Two other sources of electrical energy are pictured in Figure 17.11.

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chemical energy

Energy is stored in the bonds between atoms that make up compounds. This energy is called chemical energy, and it is a form of potential energy. If the bonds between atoms are broken, the energy is released and can do work. The wood in the fireplace in Figure 17.10 has chemical energy. The energy is released as thermal energy when the wood burns. People and many other living things meet their energy needs with chemical energy stored in food. When food molecules are broken down, the energy is released and may be used to do work.

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mechanical energy

Mechanical energy is the energy of an object that is moving or has the potential to move. It is the sum of an objects kinetic and potential energy. In Figure 17.9, the basketball has mechanical energy because it is moving. The arrow in the same figure has mechanical energy because it has the potential to move due to the elasticity of the bow. What are some other examples of mechanical energy?

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how energy changes form

Energy often changes from one form to another. For example, the mechanical energy of a moving drumstick changes to sound energy when it strikes the drumhead and causes it to vibrate. Any form of energy can change into any other form. Frequently, one form of energy changes into two or more different forms. For example, when wood burns, the woods chemical energy changes to both thermal energy and light energy. Other examples of energy conversions are described in Figure 17.16. You can see still others at this URL: http://fi.edu/guide/hughes/energychangeex.html . You can check your understanding of how energy changes form by doing the quizzes at these URLs: Energy is conserved in energy conversions. No energy is lost when energy changes form, although some may be released as thermal energy due to friction. For example, not all of the energy put into a steam turbine in Figure 17.16 changes to electrical energy. Some changes to thermal energy because of friction of the turning blades and other moving parts. The more efficient a device is, the greater the percentage of usable energy it produces. Appliances with an "Energy Star" label like the one in Figure 17.17 use energy efficiently and thereby reduce energy use.

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sound energy

The drummer in Figure 17.15 is hitting the drumheads with drumsticks. This causes the drumheads to vibrate. The vibrations pass to surrounding air particles and then from one air particle to another in a wave of energy called sound energy. We hear sound when the sound waves reach our ears. Sound energy can travel through air, water, and other substances, but not through empty space. Thats because the energy needs particles of matter to pass it on.

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electromagnetic energy

Energy that the sun and other stars release into space is called electromagnetic energy. This form of energy travels through space as electrical and magnetic waves. Electromagnetic energy is commonly called light. It includes visible light, as well as radio waves, microwaves, and X rays (Figure 17.14).

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thermal energy

The atoms that make up matter are in constant motion, so they have kinetic energy. All that motion gives matter thermal energy. Thermal energy is defined as the total kinetic energy of all the atoms that make up an object. It depends on how fast the atoms are moving and how many atoms the object has. Therefore, an object with more mass has greater thermal energy than an object with less mass, even if their individual atoms are moving at the same speed. You can see an example of this in Figure 17.13.

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instructional diagrams

No diagram descriptions associated with this lesson

questions

energy released when atomic nuclei split apart

a. chemical energy

b. electrical energy

-->  c. nuclear energy

d. thermal energy

e. electromagnetic energy

f. mechanical energy

g. sound energy

The sum of an objects kinetic and potential energy is its

a. thermal energy.

b. chemical energy.

-->  c. mechanical energy.

d. none of the above

total kinetic energy of all the atoms in an object

a. chemical energy

b. electrical energy

c. nuclear energy

-->  d. thermal energy

e. electromagnetic energy

f. mechanical energy

g. sound energy

Which form of energy travels in waves through empty space?

a. sound energy

b. electrical energy

-->  c. electromagnetic energy

d. two of the above

energy stored in chemical bonds

-->  a. chemical energy

b. electrical energy

c. nuclear energy

d. thermal energy

e. electromagnetic energy

f. mechanical energy

g. sound energy

Which energy conversion occurs in a battery?

a. electrical energy  chemical energy

b. electromagnetic energy  light energy

c. chemical energy  light energy

-->  d. chemical energy  electrical energy

Energy stored in the nucleus of an atom is called

a. electromagnetic energy.

b. electrical energy.

c. thermal energy.

-->  d. nuclear energy.

energy of an object that is moving or has the potential to move

a. chemical energy

b. electrical energy

c. nuclear energy

d. thermal energy

e. electromagnetic energy

-->  f. mechanical energy

g. sound energy

energy that travels in waves through matter from a vibrating object

a. chemical energy

b. electrical energy

c. nuclear energy

d. thermal energy

e. electromagnetic energy

f. mechanical energy

-->  g. sound energy

If two objects have the same mass, which object has greater thermal energy?

a. The object with larger atomic nuclei.

-->  b. The object with faster-moving atoms.

c. The object with faster-moving electrons.

d. The object with stronger chemical bonds.

kinetic energy of moving electrons

a. chemical energy

-->  b. electrical energy

c. nuclear energy

d. thermal energy

e. electromagnetic energy

f. mechanical energy

g. sound energy

energy that travels in electrical and magnetic waves

a. chemical energy

b. electrical energy

c. nuclear energy

d. thermal energy

-->  e. electromagnetic energy

f. mechanical energy

g. sound energy

Stars release electromagnetic energy into space.

-->  a. true

b. false

The energy stored in food is chemical energy.

-->  a. true

b. false

During photosynthesis, plants change thermal energy to chemical energy.

a. true

-->  b. false

A stretched rubber band has mechanical energy.

-->  a. true

b. false

When you plug in a lamp, electromagnetic energy is converted to light energy.

a. true

-->  b. false

Kinetic and potential energy add up to mechanical energy.

-->  a. true

b. false

There is stored chemical energy in food.

-->  a. true

b. false

A lightning bolt is a powerful discharge of light energy.

a. true

-->  b. false

Most of the electrical energy we use is produced in power plants.

-->  a. true

b. false

The sun produces nuclear energy when hydrogen nuclei undergo fusion.

-->  a. true

b. false

Some of the suns energy travels through space to heat and light Earth.

-->  a. true

b. false

The atoms that make up matter are in constant motion.

-->  a. true

b. false

Radio waves are a type of sound waves.

a. true

-->  b. false

Energy rarely changes from one form to another.

a. true

-->  b. false

One form of energy cannot change into two or more different forms of energy.

a. true

-->  b. false

Which form of energy does your body use to stay warm?

a. light energy

b. sound energy

-->  c. chemical energy

d. none of the above

Which type of energy is stored in wood?

a. thermal energy

b. light energy

-->  c. chemical energy

d. two of the above

Sources of electrical energy include

a. the sun.

b. lightning.

c. batteries.

-->  d. two of the above

Nuclear power plants produce energy by

a. burning fossil fuels.

-->  b. splitting atomic nuclei.

c. causing chemical reactions.

d. capturing kinetic energy of atoms.

The thermal energy of an object depends on

a. how quickly its atoms are moving.

b. how much light it gives off.

c. how many atoms it has.

-->  d. two of the above

Electromagnetic waves include all of the following except

a. light.

-->  b. sound.

c. X rays.

d. microwaves.

Sound waves can travel through all of the following except

a. air.

-->  b. space.

c. water.

d. glass.

diagram questions

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