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# Visualizing a Voltage

#### Guiding Questions:

• What is voltage?
• How does a generator produce a voltage?

## Step 1

For this experiment, you will need a digital interface to connect your computer with the linear generator. We provide two options for you to use: 1) PASCO 550 interface, and 2) PASCO wireless voltage sensor.

## Step 2

Connect the PASCO device with the provided analog voltage cable and connect it to the linear generator. You will then need to open up the SparkVue software that is provided with the device.

## Step 3

If you are using the PASCO wireless voltage sensor, you will need a set of banana cables to connect this to the generator.

## Step 4

Connect the wireless sensor to the generator and then open up the SparkVue software.

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# Application of a Generator

The secondary experiment is designed to illustrate the parallels between generators and motors. In this experiment, the linear motor from the previous unit is used and connected to the generator made in this unit.

#### Guiding Questions:

• How is electricity generated?

## Step 1

For this experiment, you will need the linear motor made in the previous unit, two banana cables, and the linear generator made in this unit.

## Step 2

Connect the linear generator and the motor together using the banana cables. Begin moving the generator’s armature.

What do you see? Try and explain what is happening.

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# Generating Electricity

The first laboratory activity is designed to be a primary scaffold to the understanding of generating electricity. Students must first understand the fundamentals of conductivity, voltage, current, and resistance before investigating the connection between electricity and magnetism.

#### Guiding Questions:

• What is an electromagnet?
• How is electricity generated?

## Step 1

For this lab, you will need the solenoid you’ve made and a permanent magnet. Later, you will need an iron rod to connect to the magnet.

## Step 2

In the first experiment, you will need to connect the two leads of your solenoid (with the insulation removed) to an analog current meter (ammeter). You can use alligator cables (shown in photo) to make this connection easier.

To generate electricity, shake the magnet inside the solenoid, using your hand to keep the magnet from falling out. Watch the needle on the ammeter. What do you see?

## Step 3

Now, take a piece of iron rod and 3D printed end cap. Connect the end cap to the iron rod, and connect this armature to the magnet.

In the same setup as the previous experiment, use the armature to move the magent in and out of the solenoid. The armature should give you more control over the motion of the magnet. Watch the needle on the current meter. What do you notice?

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# Building the Linear Generator

A linear generator is a simple electromagnetic device that is capable of  generating electrical current.

## Step 1

### Fabricate Generator Parts

#### Laser Cutter Files

There are three file formats (PDF, AI, SVG). Select the format that is compatible with your machine’s software.

#### Laser Cutter Material

To build the generator, we use 1/8″ baltic birch plywood (source: Inventables). If you use a different material, be sure to adjust tolerances on the CAD file.

#### 3D Printer File

There is a single file in the downloaded package (end-cap). Open the 3D printer software and import the STL file, print four end caps for the motor.

## Step 2

Assemble the laser cutter parts together to build the body of the generator. The pieces should press-fit together. A hammer can be used to tap in parts into the corresponding holes.

Press the spool holders and the end stops into the motor base.

## Step 3

Finish the assembly of the generator body by attaching the four feet to the bottom of the base. Again, use the hammer if necessary.

At this point, the generator body assembly should be completed.

## Step 4

Assemble the two banana jacks onto the generator base. There are two holes cut out towards the back that will fit the jacks. You will need to unthread the nut and remove the washer. Attach and tighten the nut and washer onto the base.

Here is how the banana jacks should look after you attach them to the base.

## Step 5

You will now need to use the solenoid made in the previous unit. There should be two trough pieces that connect to the end of the solenoid. Gather all of these pieces.

Attach the two trough pieces to each end of the solenoid. These will guide the magnet in and out of the solenoid.

Finally, attach the solenoid assembly onto the generator base. The troughs should rest on top of the generator base as shown in this photo. Guide the two ends of the solenoid wire through the small holes located below the solenoid tube on the base.

## Step 6

You will need to solder the two solenoid wires onto the terminals of the banana jacks.

To make the soldering process easier, take each wire from the solenoid, remove the red insulation coating, and wrap it around the terminals as shown in the photo. This will keep the wire in place as you try and solder it.

Finally, solder the wire to the banana jack terminal.

## Step 7

To assemble the armature of the generator, you will need a permanent magnet, piece of iron rod, and a 3D printed plastic end cap.

Connect the end cap to one side of the iron rod, hammering this in if necessary. Then connect the magnet to the end cap. This armature is what moves inside and out of the solenoid to generate electricity.

## Step 8

To make the armature easier to manuvear, you may bend the iron rod towards the end sticking out of the generator. This process creates a handle for you to use.

Your final generator should look like the photo on the left.

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## The Linear Generator Invention Kit

If the armature of a solenoid is replaced with a magnet, the magnetic can be moved in both directions by reversing the direction of the current. Reversing the direction of the current reverses the north and south poles of the electromagnet. This, in turn, moves the permanent magnet back and forth in the tube of the solenoid to create a motor. Because the magnet moves back and forth in a straight line, it is called a linear motor. A rotary motor that moves in a circle will be introduced in a later invention kit.

### Teacher Guide

The teacher package contains lesson plan documents to guide teachers through each kit and activity. In addition, everything required for constructing the invention kits is contain in this downloadable package. This includes materials, sourcing, tools, and CAD files for fabrication.

### Prior Knowledge

#### Science Content

The Linear Generator Invention Kit is scaffolded all the way down to the fundamentals of magnetism: polarity, attraction, and repulsion. Students should understand the basic functionality of a battery and common uses of electricity. Students should also be prepared to make qualitative and quantitative observations in a laboratory activity format.

#### Engineering Skills

This unit serves as an introduction to the engineering design process and utilizing digital fabrication tools. Prior to starting this unit, it will be useful for students to understand how to use 2D design software (MakerStudio by FableVision or Silhouette Studio) and operate a Silhouette Die Cutter. The technology skills in this unit can be taught in situ as students work through the laboratory activities and Design Challenge.

### Time Allotment

Failure is an important part of the engineering design process. Therefore, it is important to allocate appropriate class time to allow students to brainstorm multiple solutions, design an optimal solution, and revise their strategy/design as they progress through the engineering and fabrication process.

For an engineering-only elective with 45 minute class periods, the following time allotment is suggested. This time allotment varies based on school scheduling, pedagogical style, and technology/resource availability.

Unit Breakdown Time Allotted
Lab Activities 1-5 7 class periods
Proposal for Design Challenge 1 class period
Design Challenge 5 class periods
Presentations 1-2 class periods

### Essential Questions

How can scientific knowledge of electromagnetism be applied to create controlled motion?

How do constraints impact the design process?

Why is planning important in the engineering design process?

### Key Concepts & Skills

#### Concepts

• Conductors & Insulators
• Magnetism
• Electricity
• Electromagnetism

#### Skills

• Soldering
• Making qualitative observations
• 2D Design (MakerStudio by FableVision or Silhouette Studio)
• Fabrication on Silhouette Die Cutter