Energy Conversions

Energy Conversion

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

Most forms of energy can be converted into any other form.

A toaster converts electrical energy to thermal energy.

In an electrical motor, electrical energy is converted to mechanical energy.

Your body converts the chemical energy from the food you eat into mechanical energy so you can move and into thermal energy to keep your body temperature the same.

Sometimes, a series of conversions is needed to do a task.

Example: lighting a match

mechanical → thermal → chemical → thermal

In a car engine...

1. Electrical energy produces a spark.

2. The spark's thermal energy causes the fuel to burn releasing chemical energy.

3. When the fuel burns, the chemical energy becomes thermal energy.

4. Thermal energy becomes mechanical energy used to move the car and electrical energy used to create more sparks.

Recap...

Give an example of an energy conversion.

Potential energy → Kinetic Energy

One of the most common conversions is the conversion of potential energy to kinetic energy.

Example: jumping on a trampoline 1. jumping (kinetic) 2. stretching of trampoline (elastic potential) 3. trampoline snaps back (kinetic) 4. kinetic energy from trampoline gives you kinetic

energy to move upward

Other examples...

An earthquake converts the potential energy stored in Earth to kinetic energy at Earth's surface.

The water at the top of a waterfall has gravitational potential energy because it is higher than at the bottom. As the water falls its height decreases and it loses its potential energy. At the same time its kinetic energy increases because its velocity increases.

Pole Vaulting What are the energy conversions

during a pole vault? (kinetic or potential)

He starts off running.... He puts the pole down.... The pole straightens out and lifts him

in the air... The pole vaulter is over the bar and

begins to fall down...

Pendulum As a pendulum swings back and forth it

switches between kinetic and potential energy.

Where is the most potential energy? Where is the most kinetic energy?

Checkpoint

What energy change occurs when an object falls?

The law of conservation of energy states that when one form of energy is converted to another, no energy is destroyed in the process.

Energy cannot be created or destroyed.

Friction sometimes stops an object from moving. It can change one form of energy to thermal energy. The energy is not lost or destroyed but changed.

Example: When your hands are cold, you use friction to warm them up by rubbing your hands together. This changes mechanical energy into thermal energy.

Plants make their own food through the process of Photosynthesis. Plants use the energy from the sun to make their own food. This process takes place in the chloroplasts of their cells. (Radiant energy → chemical energy)

Radiant Energy = Electromagnetic Energy

Electromagnetic Energy = Light Energy

The plants food is stored as glucose.

Humans and other organisms do not make their own food. We get energy from stored plant food by eating plants or animals that have eaten plants. We use this energy to move, maintain body temperature and perform life functions.

Fossil Fuels

Fuels are materials that release energy when they burn.

Fossil fuels are energy rich substances formed from the remains of organisms.

Examples: gasoline, propane, coal.

The potential chemical energy in fossil fuels and food was stored by plants that converted the sun's radiant energy into chemical energy.

The process of burning fuels is known as combustion. (Potential chemical → thermal)

In a power plant...

chemical → thermal → mechanical → electrical

The electrical energy is used to light your home and run other electrical devices.