Energy: Energy: Forms and Forms and ChangesChanges

Forms of Energy

The main forms of energy are:Thermal(Heat)ChemicalElectromagnetic(light)NuclearMechanical(motion)ElectricalSound

Energy Transformations or Conversions

Most forms of energy can be transformed into other forms.

A change from one form of energy to another is called an energy transformation.

Transformations Between Potential and Kinetic Energy

One of the most common energy transformations is the transformation between potential energy and kinetic energy.

In waterfalls such as Niagara Falls, potential energy is transformed to kinetic energy.

The water at the top of the falls has gravitational potential energy.

As the water plunges, its velocity increases.

Its potential energy becomes kinetic energy.

Kinetic-Potential Energy Conversion

Roller coasters work because of the energy that is built into the system. Initially, the cars are pulled mechanically up the tallest hill, giving them a great deal of potential energy. From that point, the conversion between potential and kinetic energy powers the cars throughout the entire ride.

Kinetic vs. Potential Energy

At the point of maximum potential energy, the car has minimum kinetic energy.

Common Energy Transformations Every day, energy transformations are all around you. Some of these transformations happen inside you!

Energy and Friction So what happens to the energy of the

top? As the top spins, it encounters friction with the floor and

friction from the air.

Whenever a moving object experiences friction, some of its kinetic energy is transformed into thermal energy. (Why you cannot have perpetual motion machines)

So, the mechanical energy of the spinning top is transformed to thermal energy.

The top slows and eventually falls on its side, but its energy is not destroyed—it is transformed.

Conservation of Energy If you set a spinning top in motion, will the top

remain in motion forever? No, it will not. Then what happens to its energy? Is the energy destroyed? Again, the answer is no. The law of conservation of energy states:

Energy is not created nor destroyed only changed into other forms. The total amount of energy remains the same.

What happens when electrical energy is changed to thermal energy?

a. An energy transfer takes place.b. A force change takes place.c.An energy conversion takes place.d. An electrical conversion takes

place.

What happens when electrical energy is changed to thermal energy?

a. An energy transfer takes place.b. A force change takes place.c.An energy conversion takes place.

d. An electrical conversion takes place.

Any time an energy conversion takes place, some of the original energy is converted to which one of the following?

a. sound energyb. potential energyc. light energyd. thermal energy

Any time an energy conversion takes place, some of the original energy is converted to which one of the following?

a. sound energyb. potential energyc. light energyd. thermal energy

When you eat fruits and vegetables, which of the following types of energy are you taking in?

a. thermal energy c. electrical energyb. sound energy d. chemical energy

When you eat fruits and vegetables, which of the following types of energy are you taking in?

a. thermal energy c. electrical energyb. sound energy d. chemical energy

Which of the following is a conversion from light energy to chemical energy?

a. turning on a stove to heat dinnerb. turning on a lampc. growing an apple treed. making toast in a toaster

Which of the following is a conversion from light energy to chemical energy?

a. turning on a stove to heat dinnerb. turning on a lampc. growing an apple treed. making toast in a toaster