Shed Light on Electric Generators: Do More Coils Generate More Electricity?
|Time Required||Very Short (≤ 1 day)|
|Prerequisites||You should have the patience and dexterity to coil several layers of wire neatly (or find someone who can help you). You will also need to hook up a basic circuit. Understanding electric circuits is not a prerequisite for this science project, though it will enable a deeper understanding of the electric generator.|
|Material Availability||A kit containing all the specialty items needed for this project is available from our partner Home Science Tools.|
|Cost||Low ($20 - $50)|
|Safety||Neodymium magnets are very strong. Follow the safety guidelines in the Procedure for working with these magnets.|
AbstractThe electricity in your home probably comes from a power plant, but did you know that you can actually generate your own electricity? Wondering what it would take to light up a small light? This is your chance! In this electronics science project, you will build your own electric generator and investigate how to light up not just one, but two lights.
Build an electric generator and study how the amount of coiled wire affects the amount of electricity that is produced.
Sabine De Brabandere, PhD, Science Buddies
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Last edit date: 2019-02-02
Useful devices like electric motors, loudspeakers, and electric doorbells exist because people discovered how electricity and magnetism work together. Understanding just a few basic principles can enable you to create your own electromagnet (such as in The Strength of an Electromagnet Project Idea), your own electric motor (like the Science Buddies Build a Simple Electric Motor! Project Idea) and yes, even your own electric generator, which you will create in this science project!
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.
This science project will also involve strong permanent magnets. The following Magnetism Tutorial video will introduce you to magnets and to magnetic fields , and help you better understand this science project.
The video shows how electrical current (or a moving electrical charge) generates a magnetic field. If this is the case, could you reverse the process so that a magnetic field somehow creates electric current as well? Michael Faraday (1791–1867) and Joseph Henry (1797–1878) independently discovered it is possible; moving a permanent magnet near a closed loop of conductive wire almost always induces an electrical current in the wire. This is called magnetic induction.
For this science project, you do not need to understand the technicalities of when, how, and why this current is generated; this science project concentrates on changing the number of wraps of wire in the generator. Scientists generally refer to these wraps as "loops" of wire. Will more loops generate more electricity? Once you understand this concept, you can take your knowledge a step further and try the Science Buddies Project Idea Power Move: Manipulating Magnets to Improve Generator Output. It will give you some more background information and a glimpse at how to change the magnetic field to maximize the generated electricity.
For now, It is important to note that electricity will only be generated when the magnet is moving away from or toward the loop; if you hold a magnet perfectly still next to a wire, no electrical current will be generated. Also, when you reverse the magnet (flip the north and south poles), it will cause the current induced in the loop to flow in the other direction, as illustrated in Figure 1.
Figure 1. Moving a magnet toward a closed loop of conductive wire will almost always 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 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 Science Buddies Electricity, Magnetism, & Electromagnetism Tutorial. 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!
Working with alternating current can be tricky, especially if you connect different sets of loops (or coils) together with the goal of inducing more electricity. Pay attention as to how to connect the sets of loops (or coils) so that the currents add up (i.e. the direction of the induced current is identical in both set of loops (coils) at each given moment in time) and the peak values are produced at the same time. If the timing is off, the effect of adding several sets of loops (coils) together will not be as large. If the timing is such that the current induced in one set of loops (coil) flows in the opposite direction of the current induced in the second set of loops (coil), the induced currents could even cancel each other out, resulting in very little useful generated electricity.
Terms and Concepts
- Electrical current
- Permanent magnets
- Magnetic fields
- Alternating current (AC)
- What is electrical current?
- What is the difference between alternating and direct current?
- What is a magnetic field, how can you detect it, and how do scientists represent a magnetic field?
- Give some examples of machines that use the connection of electricity and magnetism.
- Which one the following will not induce electricity in a closed loop of conductive wire?
- Moving a permanent magnet away from a stationary closed loop.
- Moving a closed loop toward a stationary magnet.
- Moving a table on which a magnet and the closed loop are placed.
- What are the rotor, the stator, the shaft, and the armature of a generator?
- PBS Online/WGBH. (2000). AC/DC: What is the difference? Retrieved October 22, 2013, from http://www.pbs.org/wgbh/amex/edison/sfeature/acdc.html
- Brain, M.; Harris, W.; and Lamb, R. (n.d.). How Electricity Works: Generators. How Stuff Works. Retrieved October 22, 2013, from http://science.howstuffworks.com/electricity3.htm
- California Energy Commission. (2012). Energy Story Chapter 6: Turbines, Generators and Power Plants. Retrieved October 22, 2013, from http://www.energyquest.ca.gov/story/chapter06.html
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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:
- Build a Simple Electric Motor Kit (1); includes:
- Plastic tube, 1 ½ 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
- Compass (1)
- LED (light-emitting diode) (2)
- Nails (4)
- Medium screws (2)
- Note:The kit also contains enough pieces to do two additional electricity projects.
- Build a Simple Electric Motor Kit (1); includes:
You will also need to gather these items:
- Ruler or measuring tape
- Corrugated cardboard (3 pieces), 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
- Sheet of paper
- 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
Recommended Project Supplies
Safety Notes about Neodymium Magnets:
- Handle magnets carefully. Neodymium magnets (used in this science project) are strongly attracted and snap together quickly. Keep fingers and other body parts clear to avoid getting severely pinched.
- Keep magnets away from electronics. The strong magnetic fields of neodymium magnets can erase magnetic media like credit cards, magnetic I.D. cards, and video tapes. It can also damage electronics like TVs, VCRs, computer monitors, and other CRT displays.
- Keep magnets away from young children and pets. These small magnets pose a choking hazard and can cause internal damage if swallowed.
- Avoid use around people with pacemakers. The strong magnetic field of neodymium magnets can disrupt the operation of pacemakers and similar medical devices. Never use neodymium magnets near persons with these devices.
- Use the magnets gently. Neodymium magnets are more brittle than other types of magnets and can crack or chip. Do not try to machine (cut) them. To reduce the chance of chipping, avoid slamming them together. Eye protection should be worn if you are snapping them together at high speeds, as small shards may be launched at high speeds. Do not burn them; burning will create toxic fumes.
- Be patient when separating the magnets. If you need to separate neodymium magnets, they can usually be separated by hand, one at a time, by sliding the end magnet off the stack. If you cannot separate them this way, try using the edge of a table or a countertop. Place the magnets on a tabletop with one of the magnets hanging over the edge. Then, using your body weight, hold the stack of magnets on the table and push down with the palm of your hand on the magnet hanging over the edge. With a little work and practice, you should be able to slide the magnets apart. Just be careful that they do not snap back together, pinching you, once you have separated them.
- Wear eye protection. Neodymium magnets are brittle and may crack or shatter if they slam together, possibly launching magnet fragments at high speeds.
In this electronics science project, you will need to wind two iron cores—one with six layers of wire and one with four layers of wire, each with 200–250 loops 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 2 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).
Figure 2. Pictures of wire dispensers made from materials included in the kit (left) or from household materials (right).
Note: If you use materials from your kit for a wire spool dispenser, you will probably need to disassemble it once the coils have been wound at the end of the next section, as parts might be needed to build the electric generator. This is not an issue if you plan to wind both coils before building the generator. However, if you would rather first test your generator with one coil, you might want to build a wire dispenser from household materials instead.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 3 be your guide throughout the instructions.
Figure 3. 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 4.
- 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 4. 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, so when you're finished, you have four equal rectangles and the folds create a V shape with flaps, as shown in Figure 5.
- Poke a hole about 1/2 inch (1.3 cm) below the edge in the middle fold.
Figure 5. 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 3 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 6. Secure it well so your axle is sturdy. We strongly suggest you use masking tape; other tape might not create a sturdy attachment.
Figure 6. 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 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 3 shows a possible setup.
- You can now 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 7.
- 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 7. 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. 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 8.
- Put the end of the magnet wire that you want to strip inside the sandpaper sandwich, as shown in Figure 8. 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 the Science Buddies Wire Stripping Tutorial video for a demonstration if you are having trouble stripping the insulation.
Figure 8. A "sandpaper sandwich" is used to remove the insulation from the ends of the magnet wire.
- This finishes your first coil. You can choose to instantly wind your second coil (i.e. repeat steps 8–21, now only coiling four layers of magnet wire on the iron core in stead of six layers, or first build your generator and coil a second core later.
Assemble a Generator with One Coil
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 9 be your guide through the instructions.
Figure 9. 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 10.
Figure 10. 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 11. 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 11. 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 11, 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, for a variation on this science project see Make It Your Own, this can be used to install a windmill or a water wheel.
Figure 11. 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 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 12. 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 12.
- 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.
Figure 12. 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.
- Now bend one straight coil (a straight iron core with magnet wire wound around) into a U-shaped coil.
- 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 13.
Figure 13. A straight coil is bent into a U-shaped coil at the edge of a table with the force of your hand.
- Fine-tune your 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 14.
Figure 14. 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 9, 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 15. Place the nails in the same holes, making sure each nail touches one leg of the LED to create electrical connections.
Figure 15. 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.
- 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 16 as your guide.
Figure 16. 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 17.
- 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 17.
Figure 17. 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 17, 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 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.
Add a Second Coil to the Generator
In the previous section, you made a generator with one coil, one LED, and a mechanism to make the shaft turn. If you successfully wired your iron core, the generator should be able to generate enough electricity to light up one LED. In this section, you will study what happens when you add a second coil or use one coil with fewer loops.
- If you did not wire a second bendable iron core with four layers of magnet wire, do it now. Review the section Wind the Coils if you need instructions. Make sure to be thorough; a nicely wound coil is essential to create a good working generator.
- This second coil will be attached to the red side panel and will rest on a cardboard support. Use Figure 18 as your guide.
Figure 18. Generator using two coils to generate electricity. Note that some tape has been removed for the purposes of this picture, to make the cardboard support visible.
- Make a cardboard support for the second coil.
- Take a piece of cardboard and fold it back and forth several times to create a layered cardboard support for the coil. Your support will need to be approximately 3/4 inch (2 cm) high and 3/4 inch (2 cm) wide. Hold it together with masking or packaging tape. See Figure 18, above.
- Attach the support to the wooden block next to one red side panel, as shown in Figure 18, above.
- Hold the U-shaped coil in a position such that:
- The flat part between the legs of the U touches the red side panel,
- One leg of the U shape rests on the cardboard support built in the previous step, and
- The opening of your U-shaped coil goes around the rotor.
- Check if both coils will create electricity simultaneously. Remember, the coils create bursts of electricity. You will want to place the second coil so the two coils create a burst of electricity at the same time. For this to happen, magnets need to approach the coil legs at the same time and be between coil legs at the same time, as illustrated in Figure 19.
Figure 19. The figure on the left shows a drawing where the legs of both the blue and the red coil face magnets at a given moment in time. With this configuration, bursts of electricity will be produced simultaneously in both coils. In the drawing on the right, the one coil is between magnets when the other is lined up with the magnets. This configuration will not lead to simultaneous bursts of electricity created in the coils.
- Use masking tape to secure the coil in this position. You might need to use a lot of tape to secure the coil in position (as evidenced in Figure 19, above), since the neodymium magnets will create a very strong pull and push on the coil when the generator is in use.
Compare Generated Electricity Versus Coil Configuration
To evaluate how the amount of generated electricity changes when using different numbers of wire loops (or wire wraps), you will test the following coil configurations:
- Coil 1 only (this is the coil with six layers wire wraps)
- Coil 2 only (this is the coil with four layers of wire wraps)
- Connecting the end lead of coil 1 to the start lead of coil 2
- Connecting the end lead of coil 1 to the end lead of coil 2
These tests will show whether or not the generator can power one LED, the first of two LEDs placed in series, the second of two LED lights placed in series, or both LEDs placed in series.
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.
Figure 20. 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. The number of LEDs placed in series that the generator can illuminate is a measurement of the peak (or maximum) amount of voltage generated.
Consult the Electricity, Magnetism, & Electromagnetism Tutorial 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.
|Coil 1 only (6 layers of coiled wire)||Coil 2 only (4 layers of coiled wire)||End lead of coil 1 connected to start lead of coil 2||End lead of coil 1 connected to end lead of coil 2|
|1 LED||Trial 1|
|2 LEDs placed in series||1st LED||Trial 1|
|2nd LED||Trial 1|
- You will test each combination 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(s).
- Record your observations in your data table.
- To test a coil with one LED:
- Connect the start lead of one of the coils to a nail and the end lead to another nail.
- Put each of these nails together with one leg of an LED in a pair of pre-drilled holes.
- Test three times, completing steps 2.a.–2.d.
- To test a coil with two LEDs placed in series:
- Leave the leads of the coil connected to the nails.
- Take two more nails and create an electric connection using a new piece of wire that is about 3 inches (7.6 cm) long. Note: Do not forget to remove the insulation from the ends of this extra piece of wire so electricity can flow from one nail, through the wire, to the other nail.
- Place each leg of one LED in one set of pre-drilled holes, the legs of a second LED in a second pair of pre-drilled holes, making sure the flagged legs (the longer legs of the LEDs, or the positive sides of the LEDs) face the same side (e.g. away from you or both to the right), as shown in Figure 21. LEDs only allow current to pass through in one direction. For that reason, it is important to have the short leg of one LED connected with the long leg of the other LED.
- Close the circuit by:
- Placing the nail with the start lead of the coil into the first hole together with an LED leg,
- Connecting the two LEDs electrically using the extra two nails connected with the extra piece of wire (Note: If placed correctly, this should connect one flagged LED leg and one unflagged LED leg), and
- Placing the nail with the end lead of the coil into the last hole together with an LED leg.
- Test three times, completing steps 2.a.–2.d.
Figure 21. Two LEDs connected in series using two nails and an extra piece of wire. Note that the long (flagged) leg of one LED is connected to the short (unflagged) leg of the other LED.
- Connect the end lead of one coil to the start lead of the other. Remember, you flagged the end lead of each coil. Twisting the ends of the leads together will make a secure electrical connection.
- Repeat step 3 with this coil combination to test if this configuration will illuminate one LED.
- Repeat step 4 with this coil combination to test if this configuration will illuminate LEDs placed in series.
- Record your observations in your lab notebook.
- Now connect the two coils' end leads together. Choose one of the free leads as start lead and the other as end lead of the "connected coil" and test if this configuration will illuminate one LED and/or two LEDs placed in series.
- Repeat step 3 with this coil combination to test if this configuration will illuminate one LED.
- Repeat step 4 with this coil combination to test if this configuration will illuminate LEDs placed in series.
- Record your observations in your lab notebook.
- Analyze your results. Do you get consistent results over the three trials? Do your results support what you learned about how electricity is created when magnets move in the vicinity of a closed loop of wire? Read over the information in the Background tab 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: Answers to Your Science Questions advice forums.
For troubleshooting tips, please read our FAQ: Shed Light on Electric Generators: Do More Coils Generate More Electricity?.
If you like this project, you might enjoy exploring these related careers:
- 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 22 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 22. Powering a generator with a windmill.|
- You can extend your testing by adding a third coil to the generator. You could choose to make a third coil with two layers. Find out how different combinations of these three coils allow you to test configurations from 2 layers up to 12 layers with increments of 2 layers of wiring. When combining coils, make sure that coils are synchronized (or have their induced current flowing in the same direction and their peak induction at the same time).
- Explore the effect that changing the configuration of the magnets has on the induced electricity. Science Buddies Project Idea Power Move: Manipulating Magnets to Improve Generator Output will 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 that allows measuring of alternating current or voltage 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 coil 1 only, coil 2 only, coil 1 and coil 2 connected start to end, and coil 1 and coil 2 connected end to end.
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.
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).
Ask an ExpertThe Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.
Ask an Expert
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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