Take a look around you. How many machines are you aware of? Maybe you can hear a dishwasher in the kitchen. Or a vacuum cleaner being run over a carpet. Can you look out a window and see cars and buses?
These are all machines—tools that help us use energy more efficiently. They let us do more work with less labor.
The earliest machines were quite simple, but very important. So important that people still use them today. When you use nail clippers, scissors, or a bottle opener, you’re using a simple tool called a lever.
In the last 100 years or so, machines have become more and more complex. Electric motors that lift elevators and run food processors, for example, don’t use just gears, levers, and cogwheels. These modern machines are run by the flow of electrical currents.
