How magnets and coils work together—and what your shake torch can teach you about electricity
Overview
Have you ever wondered if you could create light just by shaking something in your hand? In this exciting STEM activity, students will build a shake torch—a simple flashlight that generates electricity from motion. Instead of using a regular battery, the torch uses a magnet moving through a coil of wire to produce electricity through a scientific process called electromagnetic induction.
As students shake the torch, they will see an LED light up, proving that movement can be transformed into electrical energy. This hands-on Shake Torch activity introduces children to energy conversion, magnets, coils, circuits, and renewable energy while encouraging curiosity and experimentation.
Time: 45–60 minutes
Complexity: Beginner–Intermediate
Setup: Low-cost electronics materials
Activity Materials Required
- 1 sturdy cardboard tube (paper towel roll or similar)
- Insulated enamel-coated copper wire (30–32 AWG, enough for 150–300 turns)
- 1 strong cylindrical neodymium magnet
- 1 LED (5 mm, any color)
- 1 bridge rectifier (1 A, 50 V or higher)
- 1 electrolytic capacitor (100–470 µF, 16 V or higher)
- 1 transparent plastic cup or clear plastic lid (to act as the torch lens)
- 2 small cardboard rings/discs (to hold the coil in place inside the tube)
- 2 short connecting wires
- Electrical insulation tape
- Hot glue gun (or strong craft glue)
- Sandpaper (to remove the enamel coating from the wire ends)
- Scissors
- Wire cutter or pliers
- 1 cardboard disc or plastic cap (for the back cover of the torch)
Step-by-Step Instructions
Follow these steps carefully to build your Shake Torch.
1. Prepare the cardboard tube
Take a sturdy cardboard tube (such as a paper towel roll). Make a small hole near one end of the tube. This hole will allow the coil wires to come out while keeping all the electronic components safely inside.
2. Wind the copper coil
Using insulated enamel-coated copper wire, wind 150–300 turns around a marker or small cylindrical object to create a compact coil (solenoid) that fits inside the cardboard tube. Leave about 10–15 cm of wire free at both ends.
3. Insert and secure the coil
Place the completed coil inside the tube, approximately in the middle. Use two small cardboard rings (or hot glue) on either side of the coil to hold it firmly in place so it cannot slide when the torch is shaken.
4. Bring the coil wires out
Pass both wire ends through the small hole made near one end of the cardboard tube. Remove the enamel coating from the tips of the wires using sandpaper so they can make good electrical connections.
5. Build the front circuit
Take a transparent plastic cup or clear plastic lid that fits over one end of the tube. Mount the bridge rectifier, capacitor, and LED on the inside of the transparent cover. Connect the two coil wires to the AC (~) terminals of the bridge rectifier. Connect the capacitor across the + and − terminals of the rectifier, and connect the LED across the capacitor with the correct polarity.
6. Attach the front cover
Carefully place the transparent cover onto the end of the cardboard tube where the wires come out. Tuck the circuit
neatly inside the cover and secure it with tape or glue. The LED should face outward like the front of a real flashlight.
7. Insert the magnet
Insert a strong cylindrical neodymium magnet into the opposite end of the tube. Ensure that the magnet can slide smoothly back and forth through the center of the coil without getting stuck.
8. Close the back end
Seal the back of the tube with a cardboard disc or plastic cap so the magnet remains inside while still moving freely from end to end.
9. Decorate your shake torch
Wrap the tube with colored paper, paint it, or decorate it with stickers to make it look like a real flashlight. Make sure the transparent front cover remains uncovered so the LED light can be seen clearly.
10. Shake torch and observe
Hold the torch and shake it back and forth. As the magnet moves through the coil, electricity is generated. The bridge rectifier converts it to direct current (DC), the capacitor stores a small amount of energy, and the LED lights up. Try shaking at different speeds and observe how the brightness changes.
The Science Behind the Shake Torch Activity
A shake torch works because of electromagnetic induction, a discovery made by scientist Michael Faraday.
When a magnet moves through a coil of copper wire, the magnetic field around the coil changes. This changing magnetic field pushes electrons through the wire, creating an electric current.
In this Shake Torch activity:
- Mechanical energy comes from your hand shaking the torch.
- Magnetic energy comes from the moving magnet.
- Electrical energy is generated in the copper coil.
- Light energy is produced when the LED lights up.
The faster the magnet moves through the coil, the greater the change in the magnetic field, and the more electricity is generated.
This is the same principle used in electric generators, wind turbines, hydroelectric power stations, bicycle dynamos, and hand-crank flashlights.
Pro Tip:
Use a strong magnet and wind as many neat coil turns as possible. A tightly wound coil usually produces a brighter LED because more electricity is generated.
Expected Results
Students will observe that the LED may glow faintly when the torch is shaken slowly. When shaken faster, the LED becomes brighter because more electricity is generated. If a capacitor is included, the LED may stay on for a short moment after shaking stops.
Most groups will discover that faster shaking produces brighter light and that the magnet must move through the center of the coil for the torch to work effectively.
Conclusion
The Build a Shake Torch activity transforms simple materials into an exciting demonstration of electromagnetism. By shaking the torch and watching the LED light up, students experience how motion can be converted into electricity and then into light.
More importantly, they discover that the same scientific principle powers many real-world technologies, from generators to renewable energy systems. This hands-on STEM project makes electricity visible and memorable, helping children understand that energy can change from one form into another.
Frequently Asked Questions
1. Why does the LED light up when I shake the torch?
The moving magnet changes the magnetic field inside the coil, generating electricity that powers the LED.
2. What is electromagnetic induction?
Electromagnetic induction is the process of generating electricity when a magnetic field changes around a conductor, such as a copper wire coil.
3. Why does shaking faster make the LED brighter?
Faster shaking moves the magnet through the coil more quickly, creating a larger change in the magnetic field and producing more electricity.
4. Does the shake torch need batteries?
No. The shake torch generates electricity from motion, so it can produce light without a regular battery while it is being shaken.
5. Where is this principle used in real life?
Electromagnetic induction is used in electric generators, wind turbines, hydroelectric power stations, bicycle dynamos, emergency flashlights, and hand-crank chargers.
