The following information is a single lesson in a larger project. Find more great projects here.

Lesson Overview:

Now we'll learn the basics of electricity!

## Step 1: Why We Use Electricity

Electricity is a type of energy, much like heat, gravity, or light. Electrical energy flows through conductive materials, like a metal wire. You can convert electrical energy into other forms of energy to do something interesting, like turn on a light or make some noise with a speaker.

The components you might use to do this, like speakers or light bulbs, are electrical transducers. Transducers turn electrical energy into other types of energy (like heat and light) and vice versa. Things that convert other forms of energy into electrical energy are often called sensors, and things that convert electrical energy into other forms of energy are sometimes called actuators. As you can probably imagine, we use electricity in almost every aspect of our lives!

1. The lightbulb is an electrical transducer that converts electrical energy into heat and light. Try simulating the circuit in the Workplane by pressing "Start Simulation." Click on the pushbutton to turn on the light.
2. Continue to the next step.

## Step 2: Circuits

You will be building circuits to move electricity through different components. Circuits are closed loops of wire with a power source (like a battery) and a component to do something useful with the energy, called a load.

In a circuit, electricity flows from a point of higher potential energy (usually referred to as power or +) to a point of lower potential energy. Ground (often represented with a - or GND) is the point where potential energy is lowest in the circuit. In the circuits you are building, electricity only flows in one direction. This type of circuit is called direct current, or DC.

In the picture below, the arrows indicate the direction of current flow.

In alternating current (AC) circuits electricity changes its direction 50 or 60 times a second. This is the type of electricity that comes from a wall socket.

1. Press the button on the circuit in the Workplane. Follow the path that current takes from the + terminal of the battery (red), through the circuit, to the - terminal (black).
2. Continue to the next step.

## Step 3: Current, Voltage, and Resistance

In order to talk about electrical circuits, you need to be familiar with the terms voltage, current, and resistance.

One way to imagine current flow in a circuit is to to think about a rockslide going down a cliff, as shown in the picture below. The higher the cliff, the more energy the rocks will have when they hit the bottom. The height of the cliff is like the voltage in a circuit: the higher the voltage at the energy source, the more energy you have to use.

The number of rocks is like the current in an electrical circuit. The more rocks you have, the more energy is being carried down the cliff.

The bushes are like resistors in a circuit, limiting electrical flow and converting it into mechanical energy. The rocks go through bushes on the side of the cliff, losing some energy in the process. The energy is used up to crush the bushes.

1. Review the figure - a rockslide is a metaphor for electrical current flow.
2. Current (measured in amperes, or amps; with the A symbol) is the amount of electrical charge flowing through a specific point in your circuit.
3. Voltage (measured in volts; with the V symbol) is the difference in energy across one point in a circuit and another.
4. Resistance (measured in ohms; with the Ω symbol) is how much a component impedes the flow of electrical energy.
5. Continue to the next step.

## Step 4: A Few Things About Circuits

The following concepts are a few things to keep in mind when building circuits:

1. There needs to be a complete path from the energy source (power) to the point of least energy (ground) to make a circuit. If there’s no path for the energy to travel, the circuit won’t work.
2. All the electrical energy gets used up in a circuit by the components in it. Each component converts some of the energy into another form of energy. The circuit in the Workplane uses a 9V battery -- the voltage used by the light bulb, resistor, and button will add up to 9 volts.
3. The flow of current at a specific point in a circuit will always be the same coming in and going out. In the picture below, current at (1) = current at (2) + current at (3) = current at (4)
4. Electrical current will seek the path of least resistance to ground. Given two possible paths, more of the electrical current will go down the path with less resistance. If you have a connection that connects power and ground together with no resistance, you will cause a short circuit, and the current will try to follow that path. In a short circuit, the power source and wires convert the electrical energy into light and heat, usually as sparks or an explosion. If you’ve ever shorted a battery and seen sparks, you know how dangerous a short circuit can be!
5. Continue to the next step.

## Step 5: What Is a Breadboard?

The breadboard is the primary place you will be building circuits. The one that comes in your kit is "solderless" because you don’t have to solder anything together. Instead, you plug components directly into an array of "sockets." It's sort of like LEGO in electronic form!

The main figure shows the layout of the breadboard sockets. The smaller figure, in the instructions section, shows the thin metal connectors under the top layer of plastic, which carry electricity between sockets.

1. Review the figures. The first (above) shows the breadboard socket layout, and the second (below) shows the underlying network of conductive strips. Click on the picture to enlarge it.
2. Continue to the next step.

## Step 6: Circuit Diagrams

Throughout these projects, you’ll see two views of circuits. The first is a breadboard view called the Lab View in 123D Circuits, which looks like the actual stuff in your kit.

The other is a schematic view, which is a more abstract way of showing the relationships between components in a circuit. Schematics don’t always show where components are placed relative to each other, but they show how they are connected.

Both representations of a circuit are shown in the main figure below.

1. Compare the "Breadboard View" to the "Schematic View" by clicking on the schematics view button in the menu (highlighted in blue). The circuits are identical.
2. Continue to the next step.

## Step 7: First Components: LED

Next we will review the components used in this project. If you are not already familiar with any of these components, you can find more explanation in the Components + menu by selecting All Components tab.

1. The LED, or light-emitting diode, is a component that converts electrical energy into light.
2. LEDs are polarized components, which means they only allow electricity to flow through them in one direction. The longer leg on the LED is called an anode (+ side), it will connect to power. The shorter leg is a cathode (- side) and will connect to ground. When voltage is applied in the proper direction, the LED emits light!
3. Continue to the next step.

## Step 8: First Components: Resistor

A resistor is a component that impedes the flow of electrical energy. Without the resistor, the LED would be brighter for a few moments, but quickly burn out. In the simulator, this burnout is represented as a starburst over the LED component!

1. A resistor is a component that impedes the flow of electrical energy.
2. It converts some of the electrical energy into heat. If you put a resistor in series with a component like an LED, the resistor will use up some of the electrical energy and the LED will receive less energy as a result. This allows you to supply components with only the amount of energy they need. You use a resistor in series with the LED to keep it from receiving too much current. The value, or strength, of the resistor is indicated by the colored bands on its body. Resistor color codes are covered in Project 2: Spaceship Interface.
3. The resistor affects the light bulb, as well! Try changing the value of the resistor in the Workplane by highlighting it and using the drop down menu. See what each value does to the brightness of the bulb when you push the button What is the maximum resistance you can use before the bulb does not light up at all?
4. Continue to the next step.

## Step 9: First Components: Pushbutton

A pushbutton or switch forms a connection in an electrical circuit when it is activated (or "closed"). When the button is not activated (or it is "open") it interrupts the flow of electricity, breaking the circuit.

1. When a switch is closed, it will complete a circuit. There are many types of switches. Those in your kit are called momentary switches, or pushbuttons, because they are only closed while pressure is being applied. See the diagram above for an explanation of the pushbutton. You can also try pressing and releasing the button in the Workplane to visualize its operation.
2. Continue to the next lesson to learn how to build a circuit on the breadboard!

Next Lesson:Build a Simple Circuit