Power Move: Manipulating Magnets to Improve Generator Output
AbstractThe electricity you use to power everyday devices is generated by electrical generators. These fascinating and powerful machines rely on magnets to function. Though they might seem extremely complicated, once you finish this science project, you will understand how, why, and when they generate electricity. You will build your own generator, make small changes in how exactly the magnets are placed, and test when moving magnets generate electricity.
Sabine De Brabandere, PhD, Science Buddies
Recommended Project Supplies
Build an electric generator and study how the configuration of permanent magnets affects when and how much electricity is generated.
Have you ever explored or been curious about the powerful connection between electricity and magnetism? Maybe you've built an electromagnet like the one in the science project The Strength of an Electromagnet, or you've created an electric motor in Build a Simple Electric Motor!, or perhaps you've even generated your own electricity in Human-Powered Energy. Whether you've experimented, read about, or are just curious about the relationship, this science project will give you a hands-on exploration of what matters when designing an electric generator. In order to fully understand this science project, you will need to work through some of the underlying physics before you start the hands-on portion.
Electromagnetism is the study of how electricity and magnetism work together. Both electricity and magnetism result from the movement of electrons, which are tiny particles with electric charge that whiz around inside every atom. An explanation of how these create electrical currents in conductors can be found in the Science Buddies Electricity, Magnetism, & Electromagnetism Tutorial: Electric Current.
An electric generator is a powerful machine that generates electrical current. Most use strong magnets. The Electricity, Magnetism, & Electromagnetism Tutorial: Magnetism will introduce you to magnets and magnetic fields, which are represented by field lines. Read it carefully; it will help you better understand this science project.
The tutorial explains how a magnetic field can be detected using a compass. It shows how the field lines can be made visible using iron filings, which is a fun activity you will get to do in this science project! Remember, a strong field means the magnet has a strong push or pull on magnetic material and is represented by field lines that are bunched closely together. The field is weakest where the lines are spaced farther apart.
The tutorial's technical note explains how ferromagnetic material gets magnetized as magnetic fields of tiny magnetic domains line up inside the material, making it magnetic. As you consider all the information, it might seem logical that magnetic field lines do not stop at the north or south poles; they continue inside the magnet or magnetic material to form closed loops, as shown in Figure 1. Note that the field lines get bunched together inside the magnet or ferromagnetic material, indicating a strong magnetic field.
Figure 1. Bar magnet with magnetic field lines shown inside, as well as outside, the magnet. Note there should be an equal amount (13 are shown here) of field lines inside and outside the magnet. Only seven have been drawn inside the magnet (the seven blue arrows).
The tutorial also explains how electrical current (or a moving electrical charge) generates a magnetic field and creates an electromagnet . Can you turn this around? Can a moving magnet somehow generate an electrical current in a closed loop of conducting wire? Michael Faraday (1791–1867) and Joseph Henry (1797–1878) independently discovered it is possible. The effect is called electromagnetic induction and it is exactly what you will study in this science project.
Note that if at any point, the details of how, why, and when this current is generated are too overwhelming, consider starting with the science project Shed Light on Electric Generators: Do More Coils Generate More Electricity? You will still get to generate electricity and you can study how a variation in number of loops of wire affects the generated electricity. Then you can come back to this science project whenever you feel ready.
Now, how does electromagnetic induction work? First, It is important to note that electricity will only be generated when the magnet and the closed loop of wire are moving with respect to each other. If you hold a magnet perfectly still next to a wire, no electricity will be generated. Here, it gets a little tricky. The movement of one with respect to the other is not enough. The movement needs to create a change in the number of field lines crossing the area covered by the loop. Figure 2 illustrates this idea. In Figure 2, the field lines are parallel to the area covered by the loop. Moving the magnet closer to the loop does not change the number of field lines crossing the area covered by the loop. This movement will not induce (or create) electrical current. If the field lines are perpendicular to the area covered by the loop, as shown in Figure 2.C., movement of the magnet will create a big change in the number of field lines crossing the area and induce a large amount of electrical current. Figure 2.B. illustrates the situation in between, where the field lines are at an angle with respect to the loop. Moving the magnet will induce some electrical current.
Figure 2. If the number of magnetic field lines crossing the area spanned by a closed loop of conducting wire changes, an electrical current will be induced in the wire. The straight orange arrow represents the movement of the magnet; the curved orange arrow represents the induced electrical current.
The amount of electrical current produced is proportional to the rate of change of the number of field lines passing through the loop, meaning how quickly the number of field lines passing through the loop changes over time. You can increase this by using a stronger magnet (which has a stronger magnetic field, represented by more field lines), or by moving the magnet faster, or (as explained in Figure 2) by changing the orientation of the field lines with respect to the loop.
So far, you have learned about the electrical current induced in a loop of conducting wire. Now, let us briefly look at the direction of the induced electrical current. Reversing the magnet (flipping the north and south poles) will cause the current induced in the loop to flow in the other direction, as illustrated in Figure 3. Another way to reverse the direction of the induced current is to reverse the direction of the movement (moving toward or moving away from the loop of conducting wire).
Diagram showing a magnet moving up and through a loop of conductive wire, in different orientations, to create a current in the wire. The direction of the current can either be clockwise or counter-clockwise depending on which pole of the magnet passes through the loop. When the northern pole of the magnet passes through the loop first a clockwise current is created. When the southern pole of the magnet passes through the loop first a counter-clockwise current is produced.
Figure 3. Moving a magnet toward a closed loop of conductive wire will induce an electrical current in the wire. The current will reverse direction when you reverse the poles (as shown in the figure) or when you reverse the direction in which the magnet is moving. Note that when the magnet and the loop are not moving with respect to each other, no current is induced in the loop of conductive wire.
If you bring alternating south and then north poles toward a loop of wire or move a pole to and then away from a loop of wire over and over again, the electrons keep moving back and forth (or the current keeps reversing direction), creating what is called an alternating current (AC). Before you get started, read the Electricity, Magnetism, & Electromagnetism Tutorial: DC vs AC. Then you will be ready to find out how the number of loops or wraps affects the amount of electricity generated, and light up some lights!
Terms and Concepts
- Electrical current
- Permanent magnets
- Magnetic fields
- Field lines
- Electromagnetic induction
- Rate of change
- Alternating current (AC)
- What is electrical current?
- What is the difference between alternating and direct current?
- What do magnetic field lines represent? What are some ways to draw magnetic field lines around a permanent magnet?
- Which one of the following will induce electricity in a closed loop of conductive wire?
- Moving a table on which a magnet and the loop are placed such that the magnetic field lines are perpendicular to the area covered by the loop.
- Moving the pole of a magnet along the magnetic field lines toward a loop of wire, the loop being parallel to the field lines.
- Sticking a magnetic pole through the loop so it appears at the other side of the loop.
- What are the rotor, the stator, the shaft, and the armature of a generator?
- Diffen LLC. (n.d.). AC vs. DC (Alternating Current vs. Direct Current). Retrieved March 3, 2021.
- Physics 4 kids. (n.d.). Faraday Basics. Retrieved November 2, 2013.
- GE Power. (n.d.). Electricity 101 - Learn the Basics of Production. Retrieved March 3, 2021.
These specialty items can be purchased from our partner Home Science Tools:
- Electric Motor Generator Kit (1). You will need these items from the kit:
- Plastic tube, 1½ inch (4 cm) (1)
- Magnet wire, enamel-coated (1 spool)
- Cardboard box, approximately 7–8 inches wide
- Paper clips, small (2)
- Iron cores, soft (2)
- Sandpaper, fine-grit
- Wood block, pre-drilled
- Red plastic plates for rotors (2)
- Short screws (4)
- Bolt, long (1)
- Hex nuts (3)
- Neodymium magnets (6), 1/4 inch (0.6 cm) diameter
- Compasses (2)
- LED (light-emitting diode) (1)
- Nails (2)
- Iron filings
- Medium screws (2)
- Note:The kit also contains enough pieces to do two additional electricity projects.
You will also need to gather these items:
- Ruler or measuring tape
- Corrugated cardboard (2), 14 x 2 inches (36 x 5 cm); corrugations should run parallel to the short side.
- Tape; masking tape, 1 inch available from Amazon.com
- Tape; electrical tape, 1/2 inch available from Amazon.com
- Screwdriver, Phillips
- Sheets of paper (2)
- Table with sharp 90 degree edge; table edge should be no more than 1 1/2 inches (4 cm) thick.
- Small disposable cup or tiny bucket with handle
- Optional: 1-hole puncher
- String (40 inches [1 meter]); plastic twine also works well.
- Nickels or quarters (18) or pennies (36)
- Lab notebook
- Optional: Camera
Disclaimer: Science Buddies participates in affiliate programs with Home Science Tools, Amazon.com, Carolina Biological, and Jameco Electronics. Proceeds from the affiliate programs help support Science Buddies, a 501(c)(3) public charity, and keep our resources free for everyone. Our top priority is student learning. If you have any comments (positive or negative) related to purchases you've made for science projects from recommendations on our site, please let us know. Write to us at firstname.lastname@example.org.
Neodymium magnets are very strong. Adult supervision is recommended when using them. Do not let the magnets slam together. They may pinch your fingers or crack. Keep them away from small children, pets, credit cards, and pacemakers.
In this electronics science project, you will need to wind an iron core, which will have six layers of wire, with 200–250 wraps of wire per layer. This is a lot of winding! Be patient, take your time, and we highly recommend creating a tool to help you wind neatly and efficiently (further explained later). Wiring the cores neatly into coils is essential for your generator to work well.
Build a Wire Spool Dispenser
We strongly suggest—though it is not essential—that you first build a wire spool dispenser. It will be helpful for when you wind the iron cores, as explained in the next section. Figure 4 shows two examples of homemade tools built to dispense magnet wire. You can choose to temporarily use some of the materials provided in the kit (see the figure on the left) or build a simplified version from household materials, such as a cardboard box, a pencil, masking tape, and a drinking straw (figure on the right).
A wire dispenser pictured on the left has a straw inserted into the center of a spool of wire on one end and into a plastic square on the other. The plastic square is then connected to a wooden block so that the spool is resting on the wooden block and can be spun freely. Pictured on the right, a second wire dispenser is built by inserting a straw into the center of a wire spool. The straw is then placed into an open topped cardboard box and each end of the straw is inserted into opposite walls of the box to hold it in place.
Figure 4. Pictures of wire dispensers made from materials included in the kit (left) or from household materials (right).
This video shows an alternative way to wind coils. Be sure to use the drill on the slowest setting, ask for help to hold the drill, and concentrate on winding the coils carefully one next to the other.
If you have one available, you can use a power drill to speed up the coil-winding process. You should ask an adult for help with this step.
Wind the Coils
It is very difficult to wind the iron core neatly without the help of a tool. You can transform the box in which your kit came into a coil winder with a hand crank. This will not only help you coil the wire neatly, but it will also drastically increase your efficiency.
Let Figure 5 be your guide throughout the instructions.
Figure 5. A coil winder like the one depicted here helps wind an iron core neatly with magnet wire.
- Put the box your kit comes in (or a cardboard box of approximately 7–8 inches wide) in front of you, as shown in Figure 6.
- Poke holes in the middle of both of the long side panels of the box, approximately 1/2 inch (1.3 cm) from the top edge of the box.
Figure 6. Box with hole in the middle of the long side of the box. You should do this to both long sides.
- Take two pieces of corrugated cardboard, both approximately 14 inches (36 cm) long and 2 inches (5 cm) wide. Corrugations should run parallel to the short side, so the board folds easily along this side.
- Make a fold in the middle, then unfold it.
- Fold each half in half, but in the opposite direction from which you made your first fold. When you're finished, you have four equal rectangles and the folds create a V shape with flaps, as shown in Figure 7.
- Poke a hole about 1/2 inch (1.3 cm) below the edge in the middle fold.
Figure 7. Pieces of corrugated cardboard that are folded in a V shape with flaps will help support the axle of the tool to help wind the iron cores.
- Use masking tape to attach the flaps of the V shapes to the sides of the box so the holes all line up, with the bottom points of the V shapes pointing out. Masking tape (or packaging tape) will work well here. Use Figure 5 as a guide. The V shapes are there to help keep the rotating axle stable.
- Unfold two paperclips to form an L shape. These will be used to form the axle and hand cranks.
- Connect the long side of one of the L-shaped paperclips to the bendable iron core using masking tape, covering approximately 1/8 inch (.6 cm) of the iron core with tape, as shown in Figure 8. Secure it well so your axle is sturdy. We strongly suggest you use masking tape; other tape might not create a sturdy attachment.
Figure 8. Picture showing how to connect a paperclip unfolded into an L shape with the bendable iron core using masking tape (green in this picture).
- Complete the axle.
- Poke the iron core with paperclip attached through the hole in the V-shaped corrugated cardboard, then through the hole in the box.
- Poke the long side of the other L-shaped paper clip through the other V shape and the hole in the box.
- Connect the loose paperclip to the iron core using masking tape, as described in step 5.
- This completes the axle with cranks on both sides.
- Set up your wire dispenser so the spool can easily dispense wire to the core. Figure 5 shows a possible setup.
- You can now prepare to start winding your coil. Attach the end of the magnet wire to the axle with tape. Tape it close to the start of the iron core, on top of the tape used to connect the L-shaped paperclip, keeping 8 inches (20 cm) of magnet wire free to create a lead. The type of tape used is not essential in this step. Note: A lead (pronounced "leed") is a piece of electric wire that is used to connect one electrical instrument to other electrical instruments. The end of the magnet wire you are taping to the iron core will be called the start lead of the coil.
- Start winding, neatly lining each loop next to the other, starting where the masking tape ends, as shown in Figure 9.
- The individual loops might tend to spread out as you wind the coil; use your thumb and pointer finger to make sure the turns stay tight together, one next to the other.
- Make a note of how you wind, clockwise or counterclockwise. If you are winding your second coil, make sure to wind in the same direction as you did for the first coil. Rotating in the other direction would change the direction of the induced current.
Figure 9. Loops of magnet wire placed neatly, one next to the other, around an iron core starting at a connection of the iron core with the L shape. The green masking tape holds the core and the L shape together to form the axle; the white tape holds the start lead in place.
- Wind until you reach the other end of the core where the masking tape holds the core and the other paperclip together. Now, continue winding, turning the crank in the same direction heading back. This will make your second layer of loops.
- Continue winding neatly, back and forth, one layer on top of the other, until you finished your sixth layer of loops. Note: If you are winding your second coil, stop after winding four layers.
- Use a small piece of tape to secure the last loops so all the loops stay tight.
- Cut the magnet wire, leaving a lead of 8 inches (20 cm) of wire free to make electrical connections later. This lead will be referred to as the end lead of the coil.
- Use a small piece of tape and place it around the end lead, creating a little flag. This flag will mark which lead is the end lead of the coil.
- Undo the tape that holds the start lead to the axle; also undo the masking tape that holds the core and the L shapes together to form the axle. You now have a straight coil with start and end leads.
- Strip all the insulation from the last inch (2.5 cm) of both leads so they can be used to create electrical connections:
- Fold the piece of sandpaper in half, with the rough sides facing each other, to make a "sandpaper sandwich," as shown in Figure 10.
- Put the end of the magnet wire that you want to strip inside the sandpaper sandwich, as shown in Figure 10. While softly pressing the sandpaper sandwich together, gently rub it over the last inch of the wire, back and forth.
- Give the wire a quarter turn and rub some more to remove the coating on all sides of the wire.
- The wire is stripped when you can see the copper wire underneath.
- Be careful not to press too hard when rubbing or the wire could break.
- See this Wire Stripping Tutorial video for a demonstration if you are having trouble stripping the insulation.
Figure 10. A "sandpaper sandwich" is used to remove the insulation from the ends of the magnet wire.
- Now bend the coil (or the iron core with magnet wire winded around) in a U shape.
- Protect your table with a piece of paper, placed just next to the edge of the table.
- Place 1 1/2 inches (4 cm) of coil on the paper, perpendicular to the edge of the table. Hold the coil with one hand on the table while you use your other hand to bend that side 90 degrees down. Note you might need to push quite hard to bend the coil.
- Now, place 1 1/2 inches (4 cm) of the other end of the coil on the paper, perpendicular to the edge of the table. Hold the coil with one hand on the table while you use your other hand to bend this side 90 degrees down, resulting in a U shape hanging on the edge of the table, as shown in Figure 11. Your coil is now complete.
Figure 11. A straight coil is bent into a U-shaped coil at the edge of a table with the force of your hand.
Measure the Magnetic Field Configuration Around the Coil
In this section, you will measure and draw the magnetic field configuration around a straight iron core and the U-shaped coil you just finished. Consult the Electromagnetism Tutorial video if you need help on how to execute this section.
In addition to the iron core and the coil, you will need the iron filings, at least one compass, a pen, and a couple of sheets of paper. You can use a camera to take pictures to go on your Science Fair Project Display Boards.
- Create the first magnetic field configuration, with opposite poles facing the coil or core. Note: In this section, "core" will always refer to the straight iron core that comes with your kit, and "coil" will always refer to the U-shaped coil you just wound.
- Take a bendable iron core and two neodymium magnets.
- Drop the core on a hard floor or table top, or slam it a couple of times against the palm of your hand. The sudden jarring motion of "stopping" will remove all remaining alignment of magnetic domains that might be present in this ferromagnetic material. Consult the Electricity, Magnetism, & Electromagnetism Tutorial: Magnetism if you would like to learn more about ferromagnetic materials and magnetic domains.
- Place one magnet at one end of your iron core, with a small piece of cardboard between the core and the magnet, as shown in Figure 12. Place the other magnet and piece of cardboard at the other end, making sure opposite poles face the core.
- Use your compass to check if both ends of the core are connected to opposite poles:
- Hover your compass over the core, closer to one end. Check which side of the compass needle points to the magnet on this end.
- Hover your compass over the core near the other end. Check if the other side of the compass needle points to the magnet on this end.
- If not, repeat steps 1.b. and 1.c. and check again.
Figure 12. Iron core with magnets and small pieces of cardboard at both ends. The configuration shown has opposite poles facing the core.
- Make the magnetic field visible using iron filings.
- Place a sheet of paper on top of the iron core with magnets attached. The iron core should be beneath the center of the paper atop it.
- Sprinkle iron filings evenly in a circular area of about 7 inches (18 cm) diameter in the center of the top paper.
- Shake the top paper gently or use your finger to move the iron filings gently around.
- Watch magnetic field lines appear.
- Note where iron filings align easily with the field lines. This is an indication of a strong field.
- Use your compass to confirm the direction of the field lines where needed. Note: The needle will always align with the field lines.
- Take pictures if you have a camera available.
- Draw your configuration and magnetic lines on a sheet of paper. See the drawings of the magnetic field around a bar magnet in the Electromagnetism Tutorial video if you need help on how to draw magnetic field lines.
- Make an educated guess in your lab notebook of how these field lines would continue inside the ferromagnetic material of the iron core to create closed loops. Do you expect the field to be strong (lots of field lines bunched together) or weak inside the iron core?
- Carefully remove the magnets and cardboard from beneath the paper and set them aside. The magnets will pull the filings with them, so pay attention and try not to spill the filings.
- Remove the top paper and collect the iron filings back in your tube.
- Use the field configuration obtained in previous steps to form a hypothesis of what the field might look like when you bend the core in a U shape. This step allows you to refine and test your idea.
- Drop your coil on a hard floor or table top or slam it a couple of times against the palm or your hand to remove all remaining magnetic alignment in the material.
- Connect the ends of the U-shaped coil you recently wound to the two magnets and small pieces of cardboard, as you did in step 1 if you are testing the first configuration or step 8 if you are testing the second configuration. Figure 13, below, illustrates the result.
- Use a compass to detect the direction of the field lines at a particular point. At any spot in the magnetic field, the needle of the compass will always line up with the field lines. You can put your compass on top of the coil to see the direction of the field close to the coil.
- Make a drawing of the field around the U-shaped coil.
- If you need additional information, you can use your filings to make the field lines visible around the coil. This field is a little more complicated, so make sure you use your compass, in addition to the filings!
- Make an educated guess in your lab notebook of how these field lines would continue inside the ferromagnetic material within the coil to create closed loops. Do you expect the field to be strong (lots of field lines bunched together) or weak inside the iron core?
Figure 13. U-shaped coil with magnets and small pieces of cardboard at both ends. A compass is used to detect the magnetic field orientation around the coil.
- Now you will test your second magnetic field configuration: like poles facing the core,.
- Repeat step 1, making sure like poles face the core.
- Repeat steps 2–6 for the second magnetic field configuration.
- Now test the second magnetic field configuration for the coil by repeating step 7. Be sure like poles face the coil.
- Copy the table below in your lab notebook and use your drawings to fill in your findings. Note: The "area covered by a single winding (or wrap) around the coil" refers to the cross-section of your iron core. As in this project, the core is a long cylinder, this cross section is the same for each of the 900 to 1500 windings around the core and identical to the surface of the circular base of the cylinder iron bar.
|Alternating Poles Pointing Outward||Identical Poles Pointing Outward|
|Sketch of the field lines around the U-shaped coil.|
|Identify the amount of field lines going through the area covered by a single winding. (Plenty – Few – None)|
|Identify the orientation of the area covered by a single winding and most of the field lines. (Perpendicular – at an angle – parallel)|
Assemble a Generator
Note: If you used materials from the kit to create a wire spool dispenser, you might need to disassemble part of, or your entire wire spool dispenser and repurpose the pieces as you build the generator.
Let Figure 14, below, be your guide through the instructions.
Figure 14. Finished generator using one coil and six neodymium magnets to generate electricity.
- Find the materials needed to build the basic structure: the pre-drilled wooden block, two red plastic panels, four short screws, three hex nuts, and a long bolt. All of these are shown in Figure 15, below.
Figure 15. The following items are used to build the basic structure of the generator: pre-drilled wooden block, two red plastic panels, four short screws, three hex nuts, and one large bolt.
- Attach the red side panels to the sides of the wooden block using the two pre-drilled holes on either side of the wooden block and the four short screws. Use a Phillips screwdriver to secure the panels well.
- Take the long bolt, place it through the hole of one red panel, thread two hex nuts on the bolt, place the bolt through the hole of the other red panel as far as it can go, and thread the last hex nut on the bolt. This bolt will be referred to as the shaft of your generator.
- In this step, you will use electrical tape to keep the bolt and hex nuts in place. Note electrical tape is the preferred type in this step.
- Place tape on the far end of the bolt, just inside the red panel, to thicken the screw, as shown in Figure 16, below. This will keep the bolt in place without restricting its ability to rotate, since the bolt will be the central shaft of the generator.
- The next hex nut will need to be secured in the middle between the red panels, even with the two center holes drilled in the wooden block, as shown in Figure 16, below. This hex nut will hold the magnets and serve as the rotor (or rotating part) of your generator. To secure it well, place the hex nut in this final position, rotate it about 2 mm away from its final position, place two layers of tape on the bolt just next to the hex nut and thread the hex nut back in place on the tape. The hex nut should feel sturdy mounted on the bolt.
- The second hex nut mounted between the rotor and the last red side panel will be handy to thread the rotor back in place in case it does get loose. It can be left at any position between the rotor and the red panel. In Figure 16, below, it is placed against the red panel.
- Use tape to keep the last hex nut in place on the end of the bolt outside the red panel. This hex nut should be placed more or less in the middle between the red panel and the end of the bolt. It will help thread wire around the shaft (or, see Make It Your Own for a variation on this science project where this can be used to install a windmill or a water wheel).
Diagram showing a motor and axle assembly made from two plastic panels attached to opposite sides of a flat wooden board, tape, a hex bolt and 3 hex nuts. At the top of the plastic panels, a hex bolt is inserted into pre-drilled holes in the plastic so that it is parallel to the wooden board underneath. A hex nut is placed in the center of the bolt above the center of the wooden board. Another hex nut is placed at the end of the bolt against the inside of a plastic panel. The last hex nut is placed near the end of the bolt on the outside of the plastic panel. Small pieces of tape secure the nuts, and are placed at the top of the bolt inside the plastic panel, to the side of the centered hex nut on the side near the top of the bolt, and at the end of the bolt.
Figure 16. Schematic drawing illustrating where to place the three hex nuts on the central bolt. It indicates how the central hex nut (which will serve as the rotor) is aligned with the central pre-drilled holes and how to use electrical tape to secure objects in place.
- Finish the rotor by placing six neodymium magnets on the central hex nut, one on each side with alternating poles facing outward, as shown in Figure 17, below. Using this configuration, the magnetic field felt inside the coil will flip with every 60 degrees (or one-sixth of a full turn) of the shaft.
- Stack the six neodymium magnets, one on top of another. You might want to cut out small pieces of cardboard and place them between the magnets. The cardboard will help them separate more easily.
- Peel one magnet at a time from the top of your stack. Alternate whether you attach the "top" or the "bottom" (the side that was stuck to the other magnets in the stack) to the hex nut. This will ensure that you have alternating north-south poles, as shown in Figure 17.
- You might want to approach the hex nut from the side (hovering over the central bolt) to avoid the pull and push from the other magnets already on the hex nut.
- If using six magnets is difficult, feel free to test your generator with two magnets placed 180 degrees apart on the hex nut. Make sure opposite poles face outward. Note: This configuration might provide a very dim light.
Figure 17. Six neodymium magnets, one on each side of the hex nut, serve as the rotor of the generator. The magnets are placed such that the magnetic pole facing outward alternates south - north - south - north - south - north.
- Use your compass to check if you placed your neodymium magnets correctly.
- Hold the magnet above one magnet and note the direction of the compass needle.
- Turn the shaft 60 degrees (one-sixth of a full turn) so the compass faces the next magnet. Note what happened to the needle of your compass while you made the turn. Did it flip? Can you explain why?
- Flip magnets, if needed, until the needle flips for every 60 degree turn. Make sure to check all six magnets.
- Take the U-shaped coil and fine-tune the U-shaped coil so the rotor fits just inside the opening between the legs of the U shape, leaving about 1 mm of space on either side, as shown in Figure 18, below.
Figure 18. Shape the coil so the rotor fits inside the U shape, leaving just enough space to let it turn easily. Note: The magnets might pull the U shape toward it.
- In this step, the U-shaped coil will be securely attached to the support using masking tape. Make sure the coil is securely attached to the wooden block. The magnetic forces pushing and pulling on the coil when the generator is operating can be very strong.
- Place two screws in the pre-drilled holes in the wooden block on either side of the rotor; these will hold the coil.
- Place the U-shaped coil in position, resting on the wooden block with the legs just outside the rotor.
- Use masking tape to secure the coil in place. Note electrical tape stretches a little and will not do a good job keeping the coil in place. Figure 19, above, shows a finished generator using one coil and six neodymium magnets to generate electricity.
- Electrical current can only flow in a closed loop of conductive material. The coil itself is not a closed loop. Electrical connections between the leads of the coil and an LED (light-emitting diode) will close the loop. Nails will be used to ensure good electrical connections.
- Tightly wrap the bare copper part of the start lead of the coil around one nail, and the bare copper part of the end lead around another nail. Note that the bare copper of the lead wires (this is the part where you removed the insulation) need to touch the metal of the nails to create an electrical connection.
- Prepare your LED by attaching a tape flag to the longest leg. This flag will identify the positive side of the LED (the long side). You will need this later in the science project.
- Place the two legs of an LED light in the pair of pre-drilled holes next to one of the screws holding the coil, as shown in Figure 19, below. Place the nails in the same holes, making sure each nail touches one leg of the LED to create electrical connections.
Figure 19. Electrical connections between the coil leads and an LED are created using two nails.
- Test your generator.
- Give the shaft a quick turn; does your LED light up?
- If you did not see a burst of light, try again, giving the shaft a faster turn.
- You might need to dim the light in the room to see the LED, as it might only produce a faint light. Some students need to implement a mechanism that creates fast enough bursts of rotation to generate light. The section " Test Your Generator" can help you implement such mechanism.
- If your LED does not light up:
- Check the electrical connections between the coil leads and the LED. Are the bare wires (section where insulation has been removed) touching the nails? Does each nail touch one, and only one, leg of the LED? If not, make better connections and try again.
- Make sure all the insulation of both lead ends is removed. You should be able to see the bare wire all the way around. If not, remove the remaining insulation and try again.
- In case you chose the option to use two magnets in step 5.d., test if switching to six magnets gets your LED to light up.
- If your generator is still not working, consider the care you took as you wound the coil: are your loops neatly next to each other? Did you make sure you did not reverse the direction of winding when moving from one layer to the next? If you think you weren't as careful as you could have been, you might want to rewire your coil, or check if you are able to light up an LED connecting several coils together.
- Make small adjustments where needed:
- If your shaft does not rotate easily, do some tinkering to make it rotate more freely.
- If your coil is moving while you turn the shaft, secure your coil better so it stays put when the rotor turns.
Test Your Generator
Your LED might light up when you give the shaft a quick turn. To do a scientific test, you will need to create a reproducible rotation (meaning, a rotation of similar speed and duration). It is very hard to crank your generator by hand multiple times in exactly the same way. This section describes how to create a mechanism that creates reproducible bursts of rotation using a weight. (You will find other interesting ideas, like creating a windmill or a water wheel in the Make It Your Own tab).
- If you are using a tiny bucket with a handle, you can skip this step. If you are using a disposable cup, you will need to prepare it so it can easily be attached to a string.
- Carefully make two holes with the 1-hole puncher or scissors on opposite sides of the cup, near the top edge.
- Cut a string, about 40 inches (100 cm) long and attach the string to the bucket or plastic cup such that the cup or bucket can carry a mass hanging down from the string. Use Figure 20, below, as your guide.
Figure 20. A cup or bucket hanging from a string will be used to create reproducible rotations of the generator's shaft.
- Attach the other end of the string securely to the shaft using the hex nut placed outside the red panel, as shown in Figure 21, below.
- Wrap the string one time (or a few times if your string is thin) around the shaft near the hex nut.
- Screw the hex nut over the string.
- Use tape, if needed, to further secure the string and the hex nut.
- Make sure the string does not slip, but winds up around the shaft if you turn the shaft, as shown in Figure 21, below.
Figure 21. Electric generator using a bucket in which mass can be placed to create rotation.
- Place the generator at the edge of a table, as shown in Figure 21, above. This allows the bucket to freely roll down, creating a rotation of the shaft.
- Use a mass of approximately 90 grams (g) in the bucket to create rotation. This mass is equivalent to about 18 nickels. Table 1, below, lists the mass of different United States coins so you can find a different combination of coins, if needed.
|Coin||Penny||Nickel||Dime||Quarter||Half Dollar||Presidential $1 Coin||Native American $1 Coin|
|Mass||2.50 g||5.00 g||2.27 g||5.67 g||11.34 g||8.10 g||8.10 g|
- Test your generator:
- Wind the string of the bucket all the way up.
- Fill the bucket with the mass as you hold the bucket.
- Let it roll down while looking at the LED.
- Watch if your LED lights up.
- Make adjustments where needed. For instance, if your LED was lighting up using a hand crank, but is not with your bucket, or if the shaft does not turn well with your mass, you might need to add some mass to the bucket.
Compare Generated Electricity Versus Magnet Configurations
Now you have everything in place to test your generator with two permanent magnet configurations. The configurations you are going to test are:
- The permanent magnets placed on the rotor such that alternating poles face outward.
- The permanent magnets placed on the rotor such that identical poles face outward.
This generator induces fluctuating electricity. In scientific language, this is called an alternating current in the loop, or an alternating voltage over the coil. The graph below shows how the induced electricity changes over time during a little more than 1 1/2 cycles.
Graph of electricity being generated over time from a homemade generator appears similar to a standing wave. The alternating current produced by the generator is shown in the graph, and alternates between equal positive and negative values at regular intervals.
Figure 22. A graph of induced electricity over time. The part above the time axis reflects a positive induced voltage, or a current in one direction; the part below the time axis reflects a negative voltage, or a current in the opposite direction.
Multimeters that support measurements of alternating current or alternating voltage accurate enough to be used in this electronics science project are expensive. If you have one available or can use an oscilloscope to visualize how the generated current or induced voltage changes over time, do it!
As an alternative, this science project uses a qualitative measurement, being whether or not the generator can illuminate an LED light.
Consult the Electricity, Magnetism, & Electromagnetism Tutorial: DC vs AC for a more in-depth explanation of alternating current.
- Copy the following table in your lab notebook. You will use it to record your findings.
|Alternating Opposite Poles Pointing Outward||Identical Poles Pointing Outward|
- Use alternating south and north poles facing outward for your first test configuration. This is the configuration you used to give your generator a first test (step 10 of section Assemble a Generator). The field in the coil will be created by alternating poles being close to the coil legs. Note: Depending on your choice in step 5.d. of the section Assemble a Generator, you currently have two or six magnets attached to the rotor. Note the number of magnets used for your trials down in your lab notebook.
- Test this magnetic field configuration three times. For each trial, you will:
- Wind the string of the bucket all the way up.
- Fill the bucket with the mass as you hold the bucket.
- Let it roll down while looking at the LED.
- Watch if your LED lights up.
- Record your findings in your lab notebook.
- Now remove the six magnets from the central hex nut and put them back on the hex nut so all poles facing outward are identical. The field in the coil will be created by like poles being close to the coil legs. Note: If you used two magnets in step 2, use two magnets again here, both having identical poles facing outward.
- Stack the six neodymium magnets, one on top of another, with small pieces of cardboard between the magnets. The cardboard will allow for easier separation.
- Peel one magnet at a time from the top of your stack, always attaching the same side (the side that was stuck to the other magnets in the stack, or the side that was not stuck to other magnets) to the hex nut. This will ensure you have identical poles facing outward.
- You might want to approach the hex nut from the side (hovering over the central bolt) to avoid the pull and push from the other magnets already on the hex nut.
- After you have moved all the magnets to the hex nut, use your compass to check if the poles facing outward are all identical.
- Repeat step 3 for this configuration. Don't forget to perform three trials.
- Analyze your results:
- Do you get consistent results over the three trials?
- Look back at your results noted down in the table you made similar to Table 1, listing characteristics of the magnetic field generated around the coil with the two different permanent magnet configurations. Does the result of your generator test, together with your magnetic field line identification, support what you learned about how electricity is created when magnets move in the vicinity of a closed loop of wire?
- Read over the Background information again if your results are puzzling. If it is still unclear, do not hesitate to ask your science teacher or use the Science Buddies Ask an Expert advice forums.
For troubleshooting tips, please read our FAQ: Power Move: Manipulating Magnets to Improve Generator Output.
Ask an Expert
- Try other ways to make the shaft of your generator rotate. Look at the science project Put Your Water to Work: Using Hydropower to Lift a Load to get ideas on how to build a water wheel. Figure 23 can give you ideas on how to create a windmill. Remember to glue the magnets onto your hex nut if you want to try fast rotations, in order to prevent magnets from flying off and causing a hazardous situation.
|Figure 23. Powering a generator with a windmill.|
- Study how a different number of wire loops on the coil affect the generated electricity or how you can add more coils. The Project Idea Shed Light on Electric Generators: Do More Coils Generate More Electricity? can help you get started.
- If you do have a multimeter to measure the AC current or voltage, you can study the influence of the speed at which the shaft turns on the generated electricity. Note that you might need to change the rotational speed quite a bit to be able to see a difference in the number of LEDs it can power. This should not be an obstacle if you have a multimeter available. Remember to glue the magnets onto your hex nut if you want to try fast rotations, so the magnets will not fly off and cause a hazardous situation.
- If you have an oscilloscope to visualize the change of current and voltage over time, calculate the power of the generator with the different magnet configurations.
- If you have an oscilloscope to visualize the change of current and voltage over time, study how the frequency, the peak voltage, or peak current changes with different permanent magnet configurations (two magnets, six magnets, alternating or identical poles facing outward).
Frequently Asked Questions (FAQ)
To connect the unfolded paperclip to the iron core:
- Tear off a piece of masking tape that is approximately 2 inches long.
- Lay the masking tape flat on a surface.
- Place the iron core and unfolded paperclip centered on one end of the tape, as shown in figure 1, covering approximately 1/8 inch (.6 cm) of the iron core with tape.
- Affix the paperclip to the core by folding the short end of the tape over the core and paperclip.
- Now wrap the long end of the tape around the connection.
- Twist the tape a little on the side where the paperclip sticks out to make the connection even stronger.
Figure 1. Creating a sturdy connection between the unfolded paperclip and the bendable iron core.
Use the following procedure in case you find it difficult to create a sturdy connection while the axle is partially in the coil winder:
- Attach both unfolded paperclips to the bendable iron core before placing it into the coil winder.
- Unfold one L-shaped paperclip completely so it becomes a straight line.
- Using the straight side of your axle, poke the axle (iron core with both unfolded paperclips attached) through the holes of your coil winder starting from the V-shaped corrugated cardboard, then the box, followed by the hole in the other side of the box, and finally, the hole in the last V-shaped corrugated cardboard.
- Bend the straightened paperclip back into an L shape.
- See if the axle supports (the corrugated cardboard strips that are folded in a V shape with flaps and attached to the side of your coil winder) do not move while you are winding. If they do, use more or better tape to attach them better and try again. Masking tape or packaging tape will work well here.
- If your axle is still going up and down while turning, the long side of one or both of the unfolded paperclips is probably not straight. Try to straighten it as much as you can. You might need to take the axle out of your winder to do this. Sometimes, it is easier to start with a new paperclip, unfold it, straighten it, and attach it to the core.
To get a good result with as few irregularities as possible, it is very important to wind the loops very neatly, one next to the other, when creating the first layer of loops on the bendable core. Use your thumb and pointer finger to pack individual loops tightly together in case they tend to spread out. Do the best you can for all of the following layers. Figure 2 shows some acceptable results for consecutive layers of winding.
Figure 2. Consecutive layers of winding might show increased irregularity.
- Use the palms of your hands, close to your wrist, to hold the core on the table and push the free end over.
- Use mittens or cloth to protect your hands. It might allow you to push harder without hurting yourself.
- Use leverage by putting your second hand near the end of the iron core, as far as possible away from the table edge.
- Bend slightly over the core and use your body weight to create a bigger force.
- If the table is too high for you, see if you can find a chair with a sharp 90-degree edge with a surface that is no more than 1 1/2 inches (4 cm) thick.
- Once the coil is in somewhat of a U shape, you can fold the coil a little more by pushing the legs toward each other.
If all of the above fail, you might need to ask an adult for help.
Figure 3. Illustrations of the different steps involved in bending the coil.
Next time you stack the magnets, you might want to cut out small pieces of cardboard and place them between the magnets. The cardboard will help them separate more easily.
Figure 4. A compass placed in the vicinity of a magnet indicates the magnetic poles of a magnet.
If you would like to try different magnet configurations, we advise you choose from the following options:
- Test at a slower rate of rotation, where there is no need to glue the magnets on the hex nut. In this case, the magnet configuration can be changed by switching magnets around.
- Glue the different magnet configurations on two different hex nuts, creating two rotors. Switch rotors to test the different magnet configuration at a high rate of rotation. Note that although a rotor with six neodymium magnets is advised in the science projects, you can get good results with a one coil generator and two neodymium magnets placed 180 degrees apart.
- Do both leads coming from the coil show a bare wire section, or a section where insulation has been removed? You should be able to see the bare wire all the way around. If not, remove remaining insulation and try again. Hints on how to remove insulation efficiently can be found in the procedure of the science project or in the Science Buddies Wire Stripping Tutorial.
- If you have a multimeter (any type), this step explains how to use it to narrow down which part of your generator is failing. If you do not have a multimeter, go to step 3, below. Although measurements of a DC multimeter will not be accurate due to the alternating aspect of the generated current and voltage, it can still be used to indicate whether current or voltage is present during a quick turn of the rotor. Consult the Science Buddies reference How to Use a Multimeter
if you need help using a multimeter.
- If voltage over or current through the coil is detected when making a quick turn, the circuit to the LED was somehow broken. Step 3, below, will help you further narrow down the problem.
- If the multimeter does not detect any current or voltage, skip step 3 and check the magnet configuration (step 4, below) and the wiring of the coil (step 5, below).
- Is there a closed circuit of conducting material connecting the coil and the LEDs ?
- Does the bare wire section of a coil lead touch the nail, and only the nail? You might want to wind the bare copper section of the lead a couple of times around the nail. Check this for both the start and the end lead.
- Does each nail touch one, and just one, leg of the LED?
- Is your LED working? (Check with a new light if you have one available).
- Is the magnetic field configuration favorable? Use your compass to verify if magnets are placed on the hex nut such that the magnetic poles facing outward alternate south - north - south - north - south - north.
- Hold the compass above one magnet and note the direction of the compass needle.
- Turn the shaft 60 degrees (one-sixth of a full turn) so the compass faces the next magnet.
- Note if your compass needle flipped while you made the turn. If not, flip this magnet around.
- Repeat steps 4.b.–4.c. until you have checked all six magnets.
In case you are using only two magnets, they should be placed 180 degrees apart, one with the north pole facing outward, the other with the south pole facing outward.
- If your generator is still not working, consider the care you took as you wound the coil:
- See the question above, "When winding the coils, the windings becoming increasingly less even as I add more layers." for details on what is acceptable winding. If you think you weren't as careful as you could have been, you might want to rewire your coil, or check if you are able to light up an LED with a coil consisting of four layers (if you have one) or by connecting several coils together.
- Did you make sure you did not reverse the direction of winding when moving from one layer to the next? You will need to rewire you coil in case you reversed directions while winding.
- See whether or not the leads of the second coil show a bare wire section, or a section where insulation has been removed. You should be able to see the bare wire all the way around. If you do not, remove remaining insulation and try again. Hints on how to remove insulation efficiently can be found in the procedure of the science project or in the Science Buddies Wire Stripping Tutorial.
- Check if the electrical connection between the leads of the two coils is well established. Twisting the bare sections of the leads together usually makes a good electrical connection.
- Check if the electrical connection between the lead of the second coil and the LED is well established. The bare section of the lead should touch the nail, and only the nail; the nail should touch one leg of the LED.
If all connections are well established, you will need to evaluate if the induced currents are such that they reinforce each other. Following is further explanation before we enter the practical evaluation.
This generator induces fluctuating (also called oscillating) electricity. In scientific language, this is called an alternating current in the loop, or an alternating voltage over the coil. Figure 5 shows how the induced electricity changes over time during one cycle when using one coil. Consult the Electricity, Magnetism, & Electromagnetism Tutorial for a more in-depth explanation of alternating current.
Figure 5. A graph showing how induced electricity over time changes during one cycle. The part above the time axis reflects a current in one direction; the part below the time axis reflects a current in the opposite direction.
Note the current oscillates forth and back, moving part of the time in one direction (the generated electricity is positive in the graph) and part of the time in the opposite direction (the generated electricity is negative in the graph). This happens because the magnetic field inside the coil is constantly changing as you turn the rotor.
When you add a second coil to the conductive loop, a second oscillating current is induced in the circuit and the two currents combine, as illustrated in Figure 6.
Graph of induced electric current over time for two alternating current that combine. Two individual currents are colored blue and green and the combined current is colored in black. When the currents combine the resulting current reaches higher peaks and lower troughs than each individual current.
Figure 6. A graph of induced electricity over time where two currents combine. The combined current is the current that will flow through the circuit.
The combined current will flow through the circuit. Note that if the current generated in the first coil and the current generated in the second coil move in the same direction at a moment in time, they will combine constructively and the combined current will be larger than the individual currents. This explains why the combined current (black curve) is higher than the individual currents between time markers 0 and 0.5 in Figure 6. On the other hand, when the current generated in one coil flows in one direction and the current generated in the other coil moves in the opposite direction, the currents combine destructively and the combined current is smaller than the largest individual current flowing in the circuit, as can be seen between time markers 0.5 and 1 in Figure 6.
The placement of the coils with respect to the magnets on the rotor determines when the peak currents occur and in which direction the currents flow with respect to one another.
For your generator, you want to place the two coils such that the currents always flow in the same direction so they interfere constructively and create a larger combined current. The following tips will help you do so:
- First, check if the peaks of induced current occur simultaneously; in other words, make sure the legs of the coils face magnets at the same time. In your generator:
- Rotate the rotor until two magnets are positioned between the legs of one coil.
- Keeping the rotor in this position, evaluate if there are two magnets between the legs of the other coil, as illustrated in Figure 7.
- If the answer to step 1.b is no, adjust the position of the second coil such that its legs are just outside a pair of magnets.
- Note you need at least four magnets on the rotor, and preferably six to be able to create a peak in both coils simultaneously.
- Now, make sure the induced currents flow in the same direction:
- Check if the end lead of the first coil is connected to the start lead of the next coil. Note the end lead of each coil is flagged with tape, so a flagged lead should be connected to a non-flagged lead.
- Step 2.a. assumes the coils have been wound the same way (both clockwise or both counterclockwise). If you are unsure whether you wound the coils in the same way, you might want to test both, connecting an end lead to a start lead and connecting two start leads, and see which can illuminate an LED.
- In case you are unsure which lead was the start lead and which was the end lead, test your generator by connecting the coils in different ways and evaluate which connection is able to illuminate an LED.
- Always remember to make good electrical connections by twisting the bare sections of the leads together.
Figure 7. Picture showing the placement of the coil legs with respect to the magnets on the rotor. This particular configuration will induce peak currents in both coils simultaneously. Note the generator is lying on a red side panel in this picture.
You do not need to keep this in consideration when only one LED is placed into the circuit. As the generator generates alternating current, each forth and back oscillation of current will include a time when the current can flow through the LED and a time when the current cannot. This implies the LED is constantly flashing on and off. The rate at which it is flashing is too fast for the eye to catch, so you see a slightly dimmer LED light.
The polarity of the LED starts to be important when you place two in series. The LEDs need to be arranged such that the current can pass through both or is blocked by both. To do this, connect the longer leg of one LED (this is the positive side of the LED, the leg with the tape flag) with a shorter leg of the other LED (this is the negative side of the LED).
If you like this project, you might enjoy exploring these related careers:
Contact UsIf you have purchased a kit for this project from Science Buddies, we are pleased to answer any question not addressed by the FAQ above.
In your email, please follow these instructions:
- What is your Science Buddies kit order number?
- Please describe how you need help as thoroughly as possible:
Good Question I'm trying to do Experimental Procedure step #5, "Scrape the insulation from the wire. . ." How do I know when I've scraped enough?
Good Question I'm at Experimental Procedure step #7, "Move the magnet back and forth . . ." and the LED is not lighting up.
Bad Question I don't understand the instructions. Help!
Good Question I am purchasing my materials. Can I substitute a 1N34 diode for the 1N25 diode called for in the material list?
Bad Question Can I use a different part?
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