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# Island 2  Snap Circuits Electricity: Getting into the Flow

Keep in Mind

Think about how you use electricity in a single day. Do you turn on the light in the morning? Do you keep food in a refrigerator? Are you using a computer to see this sentence right now?
Electricity is a basic part of our lives. But how does electricity work? How does it control so many things we use every day?
In this Liftoff Challenge, your challenge is to learn the basics of electricity. You will also learn how to control it in different ways by building electrical circuits. You can harness the power of electricity!

## Electricity

Electricity powers many devices we use every day. Examples are lights, motors, cell phones, and computers. If it has a plug or a battery, it uses electricity. Look around the room. How many things can you find that run on electricity?

Electricity Is Moving Electrons

Everything in the universe is made of tiny particles called atoms. Atoms are too small to see—even with a normal microscope. How small are they? Try this: use a pencil to make a single dot on a piece of paper. Can you guess how many atoms are in that dot?

Electrons move around the outside of the atom like the moon orbits around the Earth. Protons and neutrons cluster in the middle part of the atom. This is called the nucleus. In some materials, like in some electrical wires, electrons can easily separate from the rest of the atom.

Each electron has a small negative (-) electrical charge. Electrons are attracted to positive (+) charges, like protons. Think of the old saying, "opposites attract." Electrons in a wire leave their atoms and are "pulled" toward the positive end of the wire.

Electrons Can Also "Push" Each Other Around.

They do not want to be near one another. They want to be near their opposites (protons). Electrons are "pulled" to the positive end of the wire, but they also "push" each other in that same direction. They are trying to find the positive charge. This flow of electrons is called an electric current. This steady flow is the source of energy that is electricity.

Imagine a group of people trying to find seats in a movie theater. They walk through the aisle in search of empty seats. The people are like the electrons, and the seats are like the protons. The people are drawn to the seats because they know that is where they belong. Plus, they feel the pressure from the people behind them to keep moving toward the seats so that everyone can find their place.  Voltage is like the "push" or the "pressure." The pressure of the pushing on the electrons of a wire becomes the energy that powers our devices.

What Is a Circuit?

Electrons need to move around a continuous (unbroken) path to create electricity. This path is called a circuit. The wires and power cords for our devices are the paths for the electrons.

In a way, electricity is like the water that flows down a river and the circuit is the riverbed.

We can design these circuits in many different ways to control electricity for specific jobs. These jobs can be as simple as turning a light bulb on and off or as complex as controlling the flight of a rocket.

Why Do Cords Have Two Prongs?

Now think about electrical power cords. Why do you think they have two prongs? (Prongs are the metal parts that stick out of the end of the cord.)

Each prong is connected to a wire; one for the electrical current to flow from the wall outlet to the device (like a light) and another to carry the current back to the wall (completing the circuit and making it a continuous path). Plastic or rubber covers the wires to keep us safe from electrical shock. (Electricity does not travel well through these materials.)

When the switch is “on," it connects the wires to make a continuous path. The current can move through the circuit to power the light.

When the switch is “off," the circuit path is broken. The current stops flowing and the light turns off.

## All Circuits Work in the Same Way

AC vs DC Current?

Direct Current

Direct current gets its name because it describes current that always flows in one direction. DC is generated from things like solar panels and wind turbines. It can be stored in batteries as energy to be used later as DC.

Benefits - DC power is necessary for many complex electronic devices. Your phone, your TV, and your remote-controlled car all require a steady, single-direction power source to work properly with their internal electronic parts. Mobile electronics that use a battery directly use its DC power.

Alternating Current (AC)

Alternating current alternates the direction of electron movement. AC is generated using a "reverse motor" that spins to generate electricity. The United States uses AC power for all large-scale transportation of electricity, and it is what comes out of your home's outlets. AC changes direction at a rate of 60 Hertz, or 60 cycles per second. If you watched a light bulb flicker on and off at 60 Hz, it would be so fast that you would not notice it flickering.

When you plug something into an outlet in your house, it provides 60 Hz AC power and 120 V.

Benefits - AC power is easier to transport across very large distances, which is why it is widely used in the United States power grid. It is also easier to generate in power plants, including coal, nuclear, and hydroelectric power.

Converting from AC to DC

Transmitting electrical power over long distances, like from large electrical power stations to your home, requires very high voltages. Most of these high-voltage transmission lines carry between 138,000 to 765,000 V. Most of your electronic devices and appliances use between 1.5 and 24 V DC.

Voltage needs to be at a safe and usable level before it gets to your home. Reducing the voltage that enters your home from the high-voltage transmission lines is done by a transformer. Since many devices use DC power, and all outlets in your home use AC power, we also have to be able to convert between the two types once it is in your home. This is done using a rectifier, which reduces the voltage even more and changes it to DC.

You have probably seen some power cords, like those for laptops, with a black box that gets warm when it is plugged in. This is the power adapter, or rectifier, that keeps your device from being electrically damaged. Your Snap Circuits kit also has a power cord with a power adaptor that changes the outlet's 120 V AC into 6, 5, or 3 V DC.

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