Two Sides of the Same Coin! Can a Motor Light a Bulb? A Fun Science Experiment for Parents and Kids
I’m Ken Kuwako, Science Trainer. Every day is an experiment.
When you think of “generating electricity,” do you imagine massive dams or giant power plants? In reality, the same mechanism used in the heart of a power plant is hidden inside tiny toys that fit in the palm of your hand. Today, I’m going to introduce a surprising experiment that uses a simple motor—the kind found in Mini 4WD cars and hobby kits—to generate electricity in an instant. The moment that small light bulb flickers to life like magic, you will witness the scientific truth of energy transformation!
Are Motors and Generators Twins?
I previously visited an exhibit on generators at the National Museum of Nature and Science. The internal structure was clearly visible: when you turn the handle, a magnet in the center spins rapidly. Surrounding it are tightly wound coils. As the magnet moves, the magnetic flux passing through the coils changes, and you can see exactly how much electricity is being produced.
If you look at this and think, “Wait, isn’t that just like a motor?” you have a very sharp eye!
The mechanism that makes a motor spin when you apply electricity and the mechanism that generates electricity when you spin a motor’s shaft are actually two sides of the same coin. This means that even a small motor from your house can become a legitimate generator if you spin it correctly. Today, I’m sharing the Kuwako-style Motor Generation recipe, which is far easier and more reliable for lighting a bulb than the old method of winding string around the shaft!
Parent-Child Challenge: The Motor Generation Experiment
The secret to this experiment lies in the perfect friction created by a wooden stick and cloth tape.
Scientific Recipe: What You’ll Need
A motor (A small hobby motor works perfectly)
Lead wires and a light bulb (or an LED)
A long wooden stick (about 20cm)
Cloth tape
Experimental Steps
Connect the motor terminals to the light bulb using the lead wires.
Wrap the cloth tape around the wooden stick.
Gently place the taped stick onto the motor’s rotation shaft and apply light pressure.
Pull the stick quickly to spin the shaft at high speed!
The Result: An Inspiring Light in the Dark!
What happens with just this simple setup? Take a look at this video!
The moment the stick is pulled, the light bulb connected to the motor flashes bright!
The kinetic energy from your own hand is converted into light energy through the motor. Feeling this transformation firsthand is moving no matter how many times you see it.
How Does It Generate Power? The Mystery of Electromagnetic Induction
Why did a motor with no batteries connected to it produce light? The answer lies in the magnets and coils hidden inside.
1. Functioning as a Motor (Electricity → Motion) When you apply electricity, a magnetic field is generated in the coil, creating a force between it and the surrounding magnets. This makes the shaft spin, moving your models.
2. Functioning as a Generator (Motion → Electricity) Conversely, when you apply external force to spin the shaft, the coil moves inside the magnetic field. This change in the magnetic field within the coil causes electricity to flow as the system tries to counteract the change. This is called electromagnetic induction.
Most of the electricity we use every day is created using this exact principle within massive generators. Whether it’s thermal power using steam or wind power using the wind, they are all essentially spinning a shaft to create power, just like this experiment.
If you take apart a common toy, you’ll always find small magnets and coils inside. If you have an old motor that no longer works, try taking it apart to see the true form of the generator for yourself.
A simple everyday scene can turn into a grand scientific laboratory just by looking at it through the lens of science. This is the ultimate joy of learning physics!
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Making the wonders and fun of science more accessible! I’ve put together simple science experiments you can do at home and tips for success. Please take a look around! ・About the operator, Ken Kuwako: here ・For various requests (writing, lectures, science workshops, TV supervision/appearances, etc.): here ・Updates are available on X (Twitter)!
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