Who Turned on the Lights–And What Made Them Go On?


Take a quick look around your classroom. Are there lights? Are there computers? Is there a projector? If the answer is “yes” to any of these questions, then your classroom is using a type of energy: electricity!

Electricity is everywhere—but you can’t see it. The closest thing to seeing electricity is when a bolt of lightning flashes through the sky during a thunderstorm. But there aren’t any bolts of lightning in your classroom. Most of the time, we can only see what electricity does for us. And it does a lot! It turns on lights, it powers computers, and it projects images on a screen.

So what is really happening when you flip that switch in your classroom and all the lights come on? The answer often starts with coal, which is an important source of electricity. Let’s follow electricity on a journey to find out more.

How Is Electricity Made?

Coal is an important energy source because it can be used to create electricity. To turn coal into electricity, miners first have to dig coal out of the ground. Then, trucks and trains bring coal to a power plant, a big building with many moving parts. Here is what happens inside the power plant:

  1. When coal is combusted, it gets very, very hot. That heat makes water in a boiler (a big box) turn into steam.
  2. The steam moves through the air and turns the propellers of a machine called a turbine.
  3. The turbine is connected to a generator, which is where the electricity is generated.
  4. The electricity goes through a transformer, which increases the electrical power.
  5. To get from the power plant to your school, the electricity travels through power lines.

Click here to see the full interactive version of this diagram!

You’ve seen power lines, whether you realize it or not. They are those big, black wires that you sometimes see high up off the ground. These wires are sometimes underground, too.

The power lines go to a lot of places: schools, homes, office buildings, hospitals, and anywhere that needs electricity. Maybe you can even see a power line from your classroom window. The big wires you might see outside go to smaller wires inside the walls of your school.

What Are Good Sources of Electricity?

In addition to coal, electricity can come from many different sources: water, wind, sunlight, natural gas, and more. But do you know where more than 40% of the electricity in the United States comes from? If you said coal, you’re right! The great thing about getting our electricity from coal is that it can be found right here in the U.S., and there is a lot of it. In the United States, we mine more than 1 billion tons of coal every single year, and most of that coal is used to make electricity at the nation’s 500 power plants.

Electricity makes quite a journey from the power plant to your classroom. There’s a lot more involved in turning on the lights than just flipping a switch!


Be sure to see the accompanying lesson: How Much Electricity Do We Use?