Energy. What is Energy? Energy is defined as the ability to cause change. Anything that causes change must have energy to effect the change. To use energy.

Energy

What is Energy?

• Energy is defined as the ability to cause change.

• Anything that causes change must have energy to effect the change.

• To use energy means to transform one form of energy into another form of energy.

Energy Transformations

• Energy is often transformed from one form to another, usually with some loss as friction or other useless thermal energy. However, the total energy is still the same.

Lightning is the electric breakdown of air by strong electric fields and is a flow of energy.

The electric potential energy in the atmosphere changes into thermal kinetic energy, light, and sound, which are other

forms of energy.

Forms of Energy?• Energy occurs in many forms:

– Chemical energy– Thermal energy– Electromagnetic energy– Gravitational energy– Elastic energy– Nuclear energy– Solar energyThese can be classified in two main

classes of energy: Potential EnergyKinetic Energy

Potential Energy

• Potential energy is the energy stored in a body or in a system due to its position.

• Even motionless objects can have energy – energy stored in the object.

Kinetic Energy

• The kinetic energy (KE) of an object is the energy which the object possesses due to its motion. KE is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes.

Units of Energy?

• The SI unit of energy is the Joule (J), defined as a kg m∙ 2/s2, named after the British scientist James Prescott Joule, who did research to investigate the relationship of energy, mass, and velocity.

Law of Conservation of Energy

• Energy is subject to the law of conservation of energy. According to this law, energy can neither be created (produced) nor destroyed by itself. Energy can only be transformed.

Renewable Energy Sources

Nonrenewable Energy Sources

• Some energy sources can be depleted (used up) and are considered nonrenewable because they can’t be replaced by Nature.

• Nonrenewable energy sources are:– Petroleum– Natural Gas– Coal– Nuclear

Energy Consumption by Source

Relative Energy Sources to Total U.S. Consumption

The End