15.  Coal, natural gas, and petroleum are examples of this source of electricity.

These are examples of fossil fuels. Fossil fuels are a non-renewable source of energy that were formed from the remains of plants and animals that lived millions of years ago. They are used to generate electricity in power plants. Here are the steps:

1. Coal, natural gas, and petroleum are extracted from the earth through mining and drilling.

2. These fuels are then transported to power plants.

3. At the power plant, the fuels are burned. The heat from burning these fuels is used to boil water, creating steam.

4. The steam turns a turbine, which is connected to a generator.

5. As the turbine spins, it generates electricity.

6. The electricity is then transmitted through power lines to homes, businesses, and other buildings.