Introduction: (Initial Observation)
Wind and water currents are the two main sources of natural mechanical energy that are being used to produce electrical energy. Historically wind and water energy was directly being used to do works such as cutting and grinding. Mechanical energy from water or wind was often distributed among different sections of a building using shafts, gears and belts. The problem is that mechanical energy can not be transmitted to far distances.
After invention of electric generator, we were able to convert mechanical energy to electrical energy and distribute it to longer distances using wires. Electric generators are now made in different sizes and powers. With availability of electrical generators, other types of mechanical energy also were used to run these generators. In some bicycles, mechanical energy from paddling is used to generate power. In cars and other vehicles, the gas engine is being used to run the generator. Steam engines have been used in the past as a source of mechanical energy.
You can have two different approach to this project.
One is studying the mechanical systems that collect and transmits mechanical energy to an electric generator. In this case you use a small electric generator for your experiments and design and construct equipment to transmit some type of mechanical energy to the generator. Your experiment can be as simple as making a hand crank generator so you can produce electricity by hand cranking. You may also try to use wind or water energy to run your generator.
Second is studying the physics of producing electric current in a wire using a magnet. In this case you will make a generator and perform experiments to see what factors affect the amount of electricity produced by your generator.
Adult supervision, gloves, goggles and other precautions are required.
Information Gathering:
Find out about what you want to investigate. Read books, magazines or ask professionals who might know in order to learn about the effect or area of study. Keep track of where you got your information from.
Physics of creating Alternative Current Electricity
It all starts from strange properties of magnets. Magnets do not just attract certain metals!
Magnetic force is also able to push and pull electrons.
So if you move a magnet next to a copper wire, you are pushing and pulling the electrons in that wire. If the wire is in a closed circuit, movements of magnet results movements of electrons and that is what we call ELECTRICITY.
So converting mechanical energy to electrical energy is as simple as moving a magnet next to a wire (or moving a wire to cut a magnetic field).
The only problem here is that when you move a magnet next to a wire, the amount of produced electricity is too little and has no practical use. To overcome this problem you use a stronger magnet, keep it as close as possible to the wire and instead of one strand of wire you use a coil of wire. All of these contribute to the production of more electricity.
To make more electricity you move multiple magnets next to multiple coils of wire.
That is exactly what is happening in electric generators or alternators.
Single-Phase Alternator
The production of single-phase alternating current is best described by thinking of the generator as a simple bar magnet rotating inside a single coil-shaped loop of wire. When the magnet rotates, the magnetic lines of force cut through the coiled wires. The strength of the field created depends the number of these lines that are cut each second. At a constant speed, more coils of wire will be cut per second as the loop approaches the one-fourth revolution point and the generated voltage reaches a maximum at this point.
As the north pole moves from the one-fourth revolution point to the one-half revolution point, fewer wire coils are being cut per second. The voltage decreases and goes to zero at the one-half revolution point where the magnetic field is parallel to the coils of wire.
As the magnet continues to rotate, the South pole’s magnetic field cuts the coiled wires in the opposite direction, producing an opposing voltage which again builds up to a maximum at the three-fourths revolution point. As the north pole moves from three-fourths turn to one full revolution, the voltage then decreases to zero.
One complete revolution of the magnetic field is called a cycle. If there was only one coil of wire in the outer portion of the generator this would be a single phase device. By adding two additional coils of wire to the generator, we could then generate current in three individual coils or phases, or three-phase power.
Also see these two project guides that are complements to this project.
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 identify and experiment the production of electrical energy from mechanical energy.
Option 1:
Find out how different design factors in an electric generator affect the production of electricity. For example you may study:
- How does the number of wire loops on the stator affect the voltage of produced electricity? (See experiment 4)
Option 2: (not recommended as a science project. Good as an engineering project)
Experiment the mechanics of collecting the mechanical energy and transmitting it to an existing electric generator. Such experiments involve the use of gears and pulleys.
For this option I am not providing any experiments. It all depends on your craftsmanship and your skills in using tools. If you think there is something that I can help you with that, please send me a message.
Project Advisor
Identify Variables:
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.
- Independent variables is the number of loops of wire used in stator coils.
- Dependent variable is the voltage of produced electricity.
- Constants are the generator model and specification
Hypothesis:
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.
Option 1:
I think a moving magnetic field produced by a moving magnet can induce electricity in a coil of wire as long as the coil stays in the magnetic field. The amount of voltage will increase by increasing the number of loops of wire in the coil.
This hypothesis is being tested in the experiment #4
Option 2:
I think we can use turbines to get the mechanical energy of wind and water and then use belts and poleis to transmit the power to an electric generator.
What is a load?
A load is any device that consumes electricity such as a light bulb. A stronger light bulb is a bigger load. In technical terms we can say that a load is bigger if it has less electrical resistance.
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.”
In the experiments of this section we design and conduct experiments to see how a moving magnetic field may produce electricity.
Experiment 1:
Demonstration of how a changing magnetic field creates an electrical current.
To demonstrate how a changing magnetic field can create an electrical current, get a 6″ piece of 3/4″ PVC pipe and wind about 300 loops of resin insulated wire to make a coil. Leave about one foot of wire on each end. remove the insulation and connect the wires to a sensitive galvanometer or voltmeter set to show milli-volts. Then insert a cow magnet into the coil. The cow magnet is about three-inches long and a half-inch in diameter.
The cow magnet is a very powerful magnet. Keep it away from computer disks!
Hold the coil in one hand and the cow magnet in your other hand so that you can push the cow magnet back and forth inside of the coil of wire. Now push and pull the cow magnet back and forth inside of the coil of wire. Note that the needle of the meter will move only when the cow magnet is moving. If the cow magnet is inside of the coil and not moving the needle of the meter stands still. When you change the magnetic field inside the coil by pushing and pulling the cow magnet back and forth, you are generating electricity shown by the movement of the needle of the meter.
Note: A high precision digital voltmeter is the best for this experiment.
Experiment 2:
In this experiment you construct a generator consisting of a bar magnet spinning inside a coil of wire. (You may save time by buying a materials kit)
A cow magnet is a strong magnet that can be used for this project, however if you could not find a cow magnet, get a similar bar magnet.
Why do they call it cow magnet?
Because it is placed in the cows stomach to attract pieces of nails or other sharp metals that may be mixed with animal food.
The spinning magnet will be called rotor and that is the component that creates a moving magnetic field.
The rotor can be made of a block of wood about 1.25″ x 1.25″ x 0.75″. Make a 3/8″ hole in the center of it’s square side. This is for 3/8″ wood dowel to go through as the axel for the rotor. Insert the wood dowel in the hole and center the wood block on the wood dowel. Apply some wood glue while sliding the dowel back and fourth about 1/4″. Let it dry and then make a 1/2″ hole on the center of a rectangular side for cow magnet.
You may also need to apply a few drops of wood glue to hold the magnet tight. Center the magnet and let it sit again for the glue to dry.
Now you must make a box around the magnet to hold your wire coil. That will be your stator.
Use card board or balsa wood from hobby store to make a box. Make a 3/8″ hole in the center of large walls for wood dowels to go through. Balsa wood is good because you can use wood glue to connect the pieces. Since it takes time for the glue to dry, use some masking tape to hold the pieces together while the glue is being dried.
Spin the rotor to make sure that it can spin freely. It does not to be too loose because the friction force will gradually open the hole and make it easier to spin.
When the box is fully dried, you can start winding the magnet wire. Magnet wire is regular copper wire insulated with a thin layer of resin. They call it magnet wire because it is used in electromagnets.
You will need about 250 feet magnet wire AWG 28.
What is AWG?
AWG is American Wire Gauge. The higher the gauge number, the smaller the diameter and the thinner the wire.
Leave about one foot of wire and then start to wind the wire around the box. Count how many turns you are winding. You better have leather gloves on while doing this because wire will cause a lot of pressure on your hand. Wind the wire as tight as possible.
I suggest to wind about 300 turns and distribute it equally in both sides of the shaft or axel (wooden dowel). Leave another foot of wire and then cut any excess wire.
Use a sand paper to remove the insulation of about 2 inches of each end of wire.
Connect the ends of wire to a 1.5 volts light bulb.
You can now spin the axel by hand and you should see that the light blinks for a short period of time. However, if you want a continues light, you need to spin the axel at least 5 rotes per second. This can be achieved by hand cranking, or by the mechanical energy of a wind mill or water mill.
As a test we used an electric drill to spin the rotor and that produced a bright light on our 1.5 volts lamp. We also tested the voltage using a multi-meter. Our generator was producing 2 volts electricity.
Repeat the experiment with different number of loops in your coil and compare the amount of electricity. Do you get a higher voltage when you have more number of turns in your coil?
I suggest trying 50, 100, 150, 200, 250 and 300 turns of wire in your coil and record the maximum AC voltage produced with each coil.
What is the maximum voltage produced by your generator for different number of loops in your coil?
Experiment 3: Making a Model Alternator
In this experiment we make an alternator or generator that has fixed magnets and moving coil. An alternator produces alternating current (a.c.). This experiment is another way to see how Electromagnetic Induction is used in an alternator.
Safety
Normal laboratory safety rules apply.
Apparatus
- 0-100 micrometer
- 2 crocodile clips
- 2 connecting leads
Motor Kit comprising:-
- 2 50cm lengths of PVC covered copper wire
- 2m length of PVC covered copper wire
- 1 wooden block with a metal tube through the centre – one end of the metal tube is insulated with
- black insulation tape
- 1 wooden base
- 2 split pins
4 aluminum rivets - 1 metal axle
- 2 flat ceramic magnets
- A U-shaped iron yoke
- 4 small rubber rings
Diagram
Procedure:
- Remove the plastic covering from the last 5cm of the longest piece of copper wire.
- Wrap this round and round the insulated tube of the wooden block. This forms one of the two slip rings.
- Hold the bare wire in place with two of the rubber rings. Wind neatly at least ten turns on to the wooden block, finishing at the opposite end of the block from where you started.
- Cut the wire so that there is 5cm of wire left over.
- Remove the insulation from this last 5 cm and wrap it around the tube to form the other slip ring. Hold it in place with the remaining two rubber rings.
- Push the axle through the wooden block and mount it between the two split pins on the wooden base. Make sure that it spins freely.
- Strip 2cm of the plastic insulation from each end of the two shorter lengths of copper wire. These will form the brushes. Secure the brushes, with the rivets, as shown in the diagram above, one at each end. Make sure that the bared ends are each touching the slip rings.
- Place the magnets on the iron yoke with Opposite Poles facing each other. Slip the wooden base and coil between the poles of the magnets.
- Connect your alternator to the micrometer using the crocodile leads and the connecting leads.
- Spin the coil and observe what happens.
Conclusion
When the coil rotates it cuts through magnetic field lines. There is an induced current (and voltage). As the coil rotates each side moves upwards through the magnetic field and then downwards. The induced current flows first one way and then the other. The current induced is alternating.
Experiment 4: How does the number of wire loops in the stator coil affect the voltage of produced electricity?
Introduction: In this experiment you will measure the voltage produced by an electric generator with different number of wire loops in the stator. For this experiment you may make 3 identical generators with 3 different number of wire loops on the stator. For example you may try 400 loops, 300 loops and 200 loops. In the procedure described bellow only one generator is used in which you modify the number of wire loops. (In this way you will save some time and some money)
Procedure: Make a wooden generator with 400 turns of wire on the stator. Connect the two wire ends of the generator to an AC voltmeter. Use a device such as a table top electric drill to spin the rotor. Observe and record the output AC voltage. (Repeat measurements 3 times. Turn off the turn back on the turning device for each measurement)
Now unwind 100 turns of wire from the stator and cut it off. The remaining wires will be 300 loops. Connect the two wire ends of the generator to an AC voltmeter. Use the same device (such as a table top electric drill) to spin the rotor. Observe and record the output AC voltage.
Finally unwind another 100 turns of wire from the stator and cut it off. The remaining wires will now be 200 loops. Connect the two wire ends of the generator to an AC voltmeter. Use the same turning device to spin the rotor. Observe and record the output AC voltage.
For each trial test, record the amount of AC voltage you measured.
Your data table may look like this:
| Stator Wire Loops | Voltage 1 | Voltage 2 | Voltage 3 | Average Voltage |
| 400 | ||||
| 300 | ||||
| 200 |
Need a control?
Test your AC meter before each measurement. To do the test connect the red and black probes to each other and make sure that it reads 0 volts. That will suffice as a control.
Another option for control is making a similar generator that in which you will not change the number of loops of wire. This will be your control. It will show that variations in produced voltage on the experimental generator is caused by change in the number of wire loops on the stator, not any other external factor.
Since it is not affordable for all students to build a second set of generator, You can just repeat your experiments and take average from the results. For example you may measure the voltage with 400 loops of wire three times and then calculate the average. You may write the average in your results table.
Make a graph?
You can use a bar graph to visually present your results. Make 3 vertical bar and name them as “200 Turns”, “300 Turns”, and “400 Turns”. The height of each bar will represent the output voltage of generator with that number of loops on the stator. For example if the vertical bar named “400 Turns” is 3 inches tall, it means that the output voltage has been 3 Volts AC with 400 turns of wire on the stator.
Materials and Equipment:
List of material can be extracted from the experiment section. This is a sample list of materials based on the Wooden Generator Science Kit of MiniScience.com.
- Wood dowel with center 1/2″ hole
- Strong Rod magnet (1/2″ diameter)
- Insulated copper wire 23 AWG
- Miniature lamp with base
- 1/2 Square foot of basswood or any hardwood (1/8″ thickness)
The wood parts in the kit are already cut to size. You may need to do some adjustments using the sandpaper.
Additional materials you need include wood glue and multimeter:
Multimeter or Voltmeter:
Any multimeter that can measure low range AC voltage may be used to measure the output voltage of your wooden 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.
Calculations:
No calculation is required for this project, however if you do any calculations related to your experiments, analysis or conclusion, you need to write your calculations here.
Summary 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.
Conclusion:
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.
