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    Home / Science lessons / Learn About Circuits
    • Learn About Circuits

      Learn About Circuits

      What Is Electricity?

      Everything around you is made up of tiny particles called atoms. Atoms have even smaller particles inside them called electrons. Electrons always have a negative charge. When electrons move, they produce electricity! Electricity is the movement or flow of electrons from one atom to another. Don't worry if this seems complicated. It is! Electrons are called subatomic particles, which means that what they are doing is happening inside atoms, so this is pretty complicated science.

      Do you remember learning about magnets? They have positive and negative charges and opposite charges (+" and "-") are attracted to each other. Well, it's the same for electrical charges. The negatively charged electrons try to match up with positive charges in other objects.

      How do electrons move from one atom to another? They float around their atoms until they receive enough electrical energy to be pushed. The energy that makes them move comes from a power source, like a battery or electrical outlet. This works sort of the same way as water flows through a hose when you turn on the faucet. When you turn on a switch or plug in an appliance, electrons flow through wires and come out as electricity, which we sometimes call "power."

      You probably know what some electronic items use batteries and some can be plugged into a wall outlet. What's the difference? The electricity that comes from the outlets in your home is very powerful - it has lots of electrons flowing with lots of energy. It is called alternating current, or AC. Electrons in AC travel back and forth very quickly (as fast as light can travel) through wires across hundreds of miles from big power plants to outlets built into the walls of houses and buildings. Because AC current is so powerful, it can also be very dangerous. You should never touch a power line or stick your fingers or objects other than electrical plugs into outlets. You can receive a big shock that could harm you from the strong currents flowing through wires and outlets.

      Batteries provide a much less powerful form of electricity called direct current, or DC. In direct current, electrons only travel in one direction - from the negative (-) end, or terminal, to the positive (+) terminal, through the battery and back out the "-" end again. The current flowing through wires connected to batteries is much safer than AC current. It is also very useful for powering small things, like cell phones, radios, clocks, toys, and more.

      All About Circuits

      A circuit is a path that electricity flows along. If the path is broken, it is called an open circuit and the electrons can't flow all the way around. If the circuit is complete, it is a closed circuit and electrons can flow all the way around from one end of a power source (like a battery), through a wire, to the other end of the power source. In a battery circuit, the positive and negative ends of a battery need to be connected through a circuit in order to share electrons with a light bulb or other object connected to the circuit.

      A switch is something that allows you to open and close a circuit. If you turn on a light switch in your house, you are closing, or completing, the circuit. Inside the wall, the switch completes a circuit and electricity flows to the light. When you turn the light switch off, the circuit gets disconnected (now it's an open circuit), electrons stop flowing, and the light goes out.

      The negatively charged electrons we talked about above can't "jump" around to match up with positive charges - they can only move along from one atom to the next. That's why circuits have to be complete in order to work.

      Life Without Electricity

      Has the electricity ever gone out where you live? Sometimes strong wind and storms can knock down power lines (tall poles holding thick wires that electricity flows through), breaking the flow of electricity. When that happens, the electrons stop flowing and can't make it to wherever they were heading. When no electricity is flowing into your house, none of the lights or outlets will work! If it's dark outside, it will be dark inside, too. Computers, telephones, microwaves, radios, and other things that have to be plugged in to work will stop working. If you've lost power before, can you describe what it was like? Were you doing anything that got interrupted? Did you have to use candles to see? If you have never experienced a power outage before, try to think about all the things you do each day that require electricity. How would your day change if you didn't have any electricity? Are there things you you could use that are powered by batteries instead?

      Helpful Teaching Links

      • Check out this teaching tip to learn more about energy and different types of electricity.
      • This animated illustration is very helpful for understanding the difference between AC and DC.

      Science Words

      Electrons- tiny particles inside of atoms that always have a negative charge. They are what cause electricity.

      Current- electrons flowing to produce electricity.

      Open Circuit- a broken path that electrons are not able to flow along.

      Closed Circuit- an uninterrupted path that electrons can flow along from a power source back to the other end of the power source.

      For science projects related to this topic, click here.

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