card
175

energy

OLogy Series
physics
card
175

energy

OLogy Series
physics

Energy is the ability to do work. Scientists define "work" as when a force moves something. When you lift a brick, you are doing work because you are exerting a force to lift the heavy object. Energy comes in many forms, such as heat, sound, light, electric, and chemical. Energy easily changes from one form to another.

Why a Joule?
All forms of energy are measured in joules, named for the English scientist James Joule. Joule conducted groundbreaking experiments that explored the relationship between energy and work. In one experiment, he measured the temperature of water moving around a paddlewheel, showing that the friction (a form of energy) produced heat (another form of energy). Joule was so passionate about his energy experiments he spent much of his honeymoon studying the energy of a waterfall. He found that the water at the base of the waterfall was hotter than the water at the top. Again, he proved that the energy of the falling water was being converted into heat. This discovery helped prove the theory that energy is neither created nor destroyed -- it simply changes forms.

A joule is a:

unit of energy

kind of currency in Australia

precious gem worth millions of dollars

Are you right?

### Correct!

A joule is the international unit of energy. It was named after James Joule, in honor of the invaluable work he did researching heat and energy. The joule is also used as the unit for work.

In Albert Einstein's now famous formula E=mc2, "E" stands for "energy," "m" stands for "mass", and "c" stands for:

time

the speed of light

gravity

Are you right?

### Correct!

E=mc2 is short for "Energy equals mass times the speed of light squared." This formula, which implies that energy can be converted into mass (and vice versa), was the basis for Einstein's theory of relativity and the development of nuclear energy.

Chemical energy, such as oil, batteries, or the food in your stomach, is a form of kinetic, or active, energy.

or
?

### Fiction

Chemical energy is actually potential, or stored, energy. The energy in oil, batteries, and food is stored in the chemical makeup of these substances.

The total amount of energy in the Universe remains constant.

or
?

### Fact

Energy may change forms, but it cannot be created or destroyed.

energy
What it is: the ability to do work
Main kinds of energy: potential and kinetic
Main units of measurement: joules or calories
Different forms: atomic, chemical, electric, mechanical, sound, heat, and light
Characteristics: changes from one form to another; can never be destroyed

Image credits: Eric Hamilton.