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Electric Generator

How does the speed of turning rotor affect the production of electricity?

Introduction: (Initial Observation)


Electricity that we use at home is produced by electric generators. Do you know how a generators works? or how does a generator create electricity?

An electric current is created when a magnet is spun rapidly inside a coil of wire. As you see in the conceptual diagram in the right, a turbine (usually powered by water or wind) spins a magnet inside a coil

This action induces an electric current in the coil that can be used to power a light bulb.

In this project you will successfully build an electric generator that really works. Your electric generator will produce enough electricity to light up a light bulb or an LED lamp. You can easily spin the axle rod and show the light to others.

After you construct a working electric generator, you may study how different factors affect the production of electricity in a generator. In this project you will perform experiments to find out “How does the speed of a turning rotor affect the production of electricity?”.

Are you ready for this project?

Invention of electricity did not start with electric generators.

First, battery was made. Battery is a device that converts chemical energy to electricity.

For many years scientists used electricity from batteries and made electromagnet and devices that are based on electromagnet such as telegraph, microphone, speaker, buzzer, telephone and electromotor.

Then the idea came up that if you can use electricity to produce a magnet, maybe you could also use magnet to produce electricity. This is what Edison did. He used magnets to produce electricity. The device that he made is called electric generator.

Learning about electricity also should be in the same order.

You must first learn about simple electric circuits, batteries and electromagnets before trying to make an electric generator.

Key Advantages of this project:

  1. It can be tried and presented as a science project using scientific method or as a technology project.
  2. All materials for the experiments are available online and in the form of a kit. Therefore you are sure that all materials are of the right type and your project will not fail because of wrong or incompatible materials.
  3. You gain a valuable experience and the outcome is exciting.
  4. It is relatively low cost and quick. You can complete all your experiments in one weekend.

Information Gathering:

Find out about electricity and how it is produced. Read books, magazines or ask professionals who might know in order to learn about the factors that may affect the production of electricity in an electric generator. Keep track of where you got your information from.

Following are samples of information that you may find.

What is electricity and how is it made?

Electricity is moving electrons in a conductor such as a copper wire. But what can force these electrons to move? There are two different ways that electricity can be made.

First method is using a chemical reaction. For example batteries make electricity by a chemical reaction.

Second method is by using magnet. But how can magnet produce electricity?

For making electricity using magnet, check the following links for information:

Making electricity using magnet is not a simple experiment, specially if you want to produce enough electricity to light up a bulb. So most likely you are not going to make an electric generator for your project; but drawings in the above sites may be reproduced in a larger size and be used in your display.

Here is also some fundamentals:
All atoms of all elements are made of a nucleus and some electrons revolving around the nucleus in certain orbits.

In conductive material, some of these electrons can also move from one atom to the next. The key piece of information that we need to know is that electrons are sensitive to magnets and can be forced to move with a magnet.

This is the foundation of all power generators. Small power generators use an engine, similar to the engine of a car or engine of a lawn mower that spins a magnet close to a coil of wire and that forces the electrons inside the wire to move and that is electricity.

For larger productions, a wind turbine or water turbine is used to spin a large magnet next to multiple coils of wire.

In some generators, coil of wire spins between the poles of a magnet and the result is still the same or better.

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

The purpose of this project is to demonstrate the production of electricity using a moving magnet. You will show that the mechanical force from your hand or other sources can be converted to electrical energy.

If you need to conduct an experiment using scientific method, you will study this question.

How does the speed of turning rotor affect the production of electricity?

The above question can change this project from a display/ technology project to an experimental project. Students at lower grades may just do a display project; however, students in higher grades are often required to complete an experimental project.

Identify Variables: (required for higher grades)

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.

For question number 1:

  • Independent variable is the speed of turning rotor
  • Dependent variable is the production of electricity, measured and described by voltage
  • Constants are the generator model and specification

Hypothesis: (required for higher grades)

Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis. Following is a sample hypothesis:

Amount of electricity made using magnet has a direct relation with the speed of magnet or moving magnetic field. The faster the rotor spins, the more voltage must be produced. My hypothesis is based on my common sense and observations of a bicycle generator that loses its light when the bicycle slows down.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”



Experiment 1: Making an Electric Generator.

Introduction: For your experiment, you may make an electric generator that really works and can light up a light bulb. There is a good design at MiniScience.com that you may use. It is called wooden generator and it consists of a small box, a coil of wire wrapped over the box and a magnet spinning inside the box. Complete materials may be purchased as a kit or purchase separately.


Following are the material that you need in order to construct a wooden electric generator.

  1. Wood dowel 3/8″ diameter
  2. Wood Dowel 1″ diameter.
  3. Strong Rod magnet (1/2″ diameter)
  4. Insulated copper wire 23 AWG, or 27 AWG 200 feet
  5. Low voltage, low current lamp with base
  6. Small sand paper
  7. Wood Glue
  8. 1/2 Square foot of balsa wood or any hardwood (1/8″ diameter)
  9. AC Voltmeter (AC=Alternative Current)
  10. Necessary wood working tools (if you are not buying a kit).


If you are buying a kit, all the wooden parts are included and they are already cut to the size. So you just need to connect them. If you don’t have a kit, prepare the wooden parts as follows:

  1. Cut two square pieces from the balsa wood (3.5″ x 3.5″).
  2. Make a 3/8″ hole in the center of each square.
  3. Cut four 1″ x 3 7/16.
  4. Cut a 3/4″ piece from the 1″ wood dowel. Make a 3/8″ hole in the center of it. Insert a 6″ long 3/8″ wood dowel in the hole, apply some glue. center it and wait for it to dry.
  5. Make another hole with the diameter of your rod magnet in the center of the larger wood dowel piece for the magnet to go through.

Wood dowels after completing the step 4

Wood dowels after completing the step 5


  1. Insert the magnet in the hole of the wood dowel. Center it and use some glue to secure it.
  2. Use one large square balsa wood and four smaller rectangular balsa woods to make a box.
  3. Insert your wood dowel into the hole in the center of the box. At this time the magnet is inside the box.
  4. Place the other large square to complete the box. Apply some glue to the edges and wait for the glue to dry. By now, you have a box and inside the box you have a magnet that can spin when you spin the wood dowel.
  5. Wrap 300 turns of copper wire around the box and use masking tape to secure it. (If you divide the wire equally, you will have 150 turns of wire in each side of the wood dowel. If you buy a kit, use all the wire included in the kit. DO NOT CUT THE WIRE) .
  6. Remove the insulation from the ends of the wire and connect them to the lamp holder or base.
  7. Insert the lamp in the lamp holder and base. Tighten the screws as needed.
  8. Spin the wood dowel fast to get the light.

More Details:

This is similar to my final sample. In order to get light I had to turn it fast.

More detail instructions are available at MiniScience.com website.

Experiment 2: How does the speed of turning rotor affect the production of electricity?

Connect the two wire ends of your generator to an AC voltmeter and use a device such as a multi speed electric drill set to test the output voltage of your generator.

For each trial test, record the amount of AC voltage you get in each speed.

Your data table may look like this:

Turning Speed Voltage 1 Voltage 2 Voltage 3 Average Voltage

Need a control?

You may use another identical generator that is connected to another AC voltmeter, but do not spin the rotor at all. This will be your control. It will show that all produced voltage on the experimental generator is caused by turning the rotor, not any other external factor.

Since it is not affordable for all students to build a second set of generator and use a second volt-meter, You can just repeat your experiments and take average from the results. For example you may measure the voltage in low speed three times and then calculate the average. You may write the average in your results table.

Materials and Equipment:

  • Wooden strips and wood dowel (Also available as a kit)
  • Magnet wire (This is just a resin coated copper wire, You can use any other shielded copper wire instead.)
  • Bar magnet (I selected a bar magnet, because it is easier to keep in hand and move. Mine was about 3 inches long, but there are many other sizes available in hardware stores.
  • A small Light bulb with base. (1.2 Volts bulb is the best and you will have more chance to see some light)
  • An AC Voltmeter to measure the output voltage
  • A multi speed electric drill that can be used to spin the rotor at different speeds.

Where to buy the materials?
Always compare the prices and qualities to make sure you will get the most for your money. I think you will save time and money if you buy everything from one place. A complete materials set for experiment 2 is available at MiniScience.com. If you want to purchase locally, magnet wire may be purchased from “Motor/Generator repair shops”; Wood may be purchased from craft stores. Magnet is available at industrial supply shops and some farm suppliers.

Multimeter or Voltmeter:

Any multimeter that can measure low range AC voltage may be used to measure the output voltage of your electric generator. Two common models are AMM360 and YG188.

Multimeter model YG188:

YG188 is an analog multimeter for general electrical use.

  • 16 Position rotary function and range selector.
  • Measures AC/DC Voltage, DC Current and resistance
  • Integrated test leads.
  • Includes rugged holster and full instructions.

Multimeter model AMM360:

AMM360 is a desktop analog multitester for measuring DC Volt, AC Volt, DC Current and Resistance. AMM360 can be used as a very sensitive galvanometer and can show as low as 0.01 DC voltage. AMM360 can also be used to test transistors and diodes.

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.

Your results table may look like this:

Turning Speed Output Voltage


If you are running multiple trials to measure the voltage for each speed, then you will need to calculate the average voltage for each speed.

Summery of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.


Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.


Visit your local library and find books related to electricity. Most such books can be used as references for this project. List the books, magazines and the websites you use in your bibliography.